Radiography device, radiography method, and radiography program

ABSTRACT

A radiography device includes: a radiation emitting unit that irradiates a subject with radiation at a plurality of different incident angles; a radiographic image generation unit that receives the radiation passed through the subject and generates a radiographic image; a part-of-interest detection unit that detects a mutation site suspected as a lesion from the radiographic image obtained by irradiating the subject with the radiation at a predetermined incident angle; and a radiography device control unit that controls whether to perform each of the tomosynthesis imaging in which the radiographic image generation unit generates the radiographic image while the radiation emitting unit changes the incident angle of the radiation and two-dimensional radiography in which the radiation emitting unit is fixed to a predetermined incident angle and the radiographic image generation unit generates the radiographic image, on the basis of a detection result of the part-of-interest detection unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of InternationalApplication No. PCT/JP2014/078526, filed on Oct. 27, 2014, thedisclosure of which is incorporated herein by reference in its entirety.Further, this application claims priority from Japanese PatentApplication No. 2013-239143, filed on Nov. 19, 2013, the disclosure ofwhich is incorporated by reference herein in its entirety.

BACKGROUND

Field of the Invention

The present invention relates to a radiography device, a radiographymethod, and a radiography program storage medium.

Description of the Related Art

A radiography device is known which captures radiographic images formedical diagnosis. An example of this type of radiography device is amammography device which captures an image of the breast of a subjectfor the early detection of breast cancer. In addition, in mammography, atomosynthesis imaging technique is known which irradiates the breast ofthe subject with radiation at different angles to capture images of thebreast. The tomosynthesis imaging technique reconstructs a plurality ofradiographic images, which are captured by irradiating the subject withradiation at different incident angles with respect to a radiationdetection surface in a predetermined range, to generate tomographicimages.

For example, U.S. Pat. No. 7,831,296B discloses a technique whichperforms mammography and tomosynthesis imaging using one process ofcompressing the breast.

In the technique disclosed in U.S. Pat. No. 7,831,296B, mammography(two-dimensional radiographic image) and tomosynthesis imaging areperformed by one process of compressing the breast. However, in somecases, it is not necessary to perform two imaging methods. Therefore,the technique needs to be improved.

SUMMARY

The invention has been made in view of the above-mentioned problems andan object of the invention is to provide a radiography device, aradiography method, and a radiography program which can obtain anaccurate radiographic image while reducing a burden on a subject.

According to a first aspect of the invention, there is provided aradiography device that is capable of perform tomosynthesis imaging. Theradiography device comprises: a radiation emitting unit that is capableof irradiating a subject with radiation at a plurality of differentincident angles; a radiographic image generation unit that receives theradiation which has been emitted from the radiation emitting unit andpassed through the subject and generates a radiographic image indicatingthe subject; a part-of-interest detection unit that detects a mutationsite suspected as a lesion from the radiographic image of the subjectwhich is obtained by irradiating the subject with the radiation emittedfrom the radiation emitting unit at a predetermined incident angle; anda radiography device control unit that controls, on the basis of adetection result of the part-of-interest detection unit, whether toperform each of the tomosynthesis imaging in which the radiographicimage generation unit generates a radiographic image while the radiationemitting unit changes the incident angle of the radiation, andtwo-dimensional radiography in which the radiation emitting unit isfixed to a predetermined incident angle and the radiographic imagegeneration unit generates a radiographic image.

According to the above-mentioned aspect, the radiation emitting unit canirradiate the subject with radiation at a plurality of differentincident angles. The radiographic image generation unit receives theradiation which has been emitted from the radiation emitting unit andpassed through the subject and generates the radiographic imageindicating the subject.

The part-of-interest detection unit detects the mutation site suspectedas a lesion from the radiographic image of the subject obtained byirradiating the subject with the radiation emitted from the radiationemitting unit at the first incident angle.

Then, the radiography device control unit controls whether to performeach of the tomosynthesis imaging in which the radiographic imagegeneration unit generates the radiographic image while the radiationemitting unit changes the incident angle of the radiation and thetwo-dimensional radiography in which the radiation emitting unit isfixed to the predetermined incident angle and the radiographic imagegeneration unit generates the radiographic image, on the basis of thedetection result of the part-of-interest detection unit. Therefore, itis possible to obtain a more accurate radiographic image while reducinga burden on the subject, as compared to a case in which bothtomosynthesis imaging and two-dimensional radiography are alwaysperformed.

The radiography device control unit may perform control such that thetomosynthesis imaging is not performed and the two-dimensionalradiography is performed in a case in which the part-of-interestdetection unit detects only the mutation site suspected as acalcification. The radiography device control unit may perform controlsuch that the two-dimensional radiography is not performed and thetomosynthesis imaging is performed in a case in which thepart-of-interest detection unit detects only the mutation site suspectedas a tumor mass.

In this case, the radiography device control unit may further performcontrol such that both the tomosynthesis imaging and the two-dimensionalradiography are performed in a case in which the part-of-interestdetection unit detects both the mutation site suspected as acalcification and the mutation site suspected as a tumor mass.

In this case, the radiography device may generate the radiographicimages with at least two types of resolution. The radiography devicecontrol unit may perform control such that the two-dimensionalradiography is performed at a second resolution higher than a firstresolution in a case in which the part-of-interest detection unitdetects at least one of the mutation site suspected as a calcificationor the mutation site suspected as a tumor mass from the radiographicimage of the subject with the first resolution which is obtained byirradiating the subject with the radiation at the first incident angle.In this case, the radiography device control unit may further performcontrol such that the tomosynthesis imaging is performed at the secondresolution higher than the first resolution in a case in which thepart-of-interest detection unit detects the mutation site suspected as atumor mass.

The radiography device control unit may perform control such that thetwo-dimensional radiography is not performed and the tomosynthesisimaging is performed in a case in which the part-of-interest detectionunit does not detect the mutation site.

In this case, the radiography device may perform the tomosynthesisimaging in at least two types of incident angle ranges. (a) Theradiography device control unit may perform control such that thetwo-dimensional radiography is not performed and the tomosynthesisimaging is performed in a first incident angle range in a case in whichthe part-of-interest detection unit does not detect the mutation site.(b) The radiography device control unit may perform control such thatthe tomosynthesis imaging is not performed and the two-dimensionalradiography is performed in a case in which the part-of-interestdetection unit detects only the mutation site suspected as acalcification. (c) The radiography device control unit may performcontrol such that the two-dimensional radiography is not performed andthe tomosynthesis imaging is performed in a second incident angle rangewider than the first incident angle range in a case in which thepart-of-interest detection unit detects only the mutation site suspectedas a tumor mass. (d) The radiography device control unit may performcontrol such that the tomosynthesis imaging is performed in the secondincident angle range and the two-dimensional radiography is performed ina case in which the part-of-interest detection unit detects both themutation site suspected as a calcification and the mutation sitesuspected as a tumor mass.

In this case, (a1) the radiography device control unit may performcontrol such that the tomosynthesis imaging is performed at a firstresolution and in the first incident angle range in a case in which thepart-of-interest detection unit does not detect the mutation site. (b1)The radiography device control unit may perform control such that thetwo-dimensional radiography is performed at a second resolution higherthan the first resolution in a case in which the part-of-interestdetection unit detects only the mutation site suspected as acalcification. (c1) The radiography device control unit may performcontrol such that the tomosynthesis imaging is performed at the secondresolution higher than the first resolution and in the second incidentangle range wider than the first incident angle range in a case in whichthe part-of-interest detection unit detects only the mutation sitesuspected as a tumor mass. (d1) The radiography device control unit mayperform control such that the tomosynthesis imaging is performed at thesecond resolution and in the second incident angle range and thetwo-dimensional radiography is performed at the second resolution in acase in which the part-of-interest detection unit detects both themutation site suspected as a calcification and the mutation sitesuspected as a tumor mass.

The radiography device control unit may perform control such thatneither the tomosynthesis imaging nor the two-dimensional radiography isperformed and imaging is stopped in a case in which the part-of-interestdetection unit does not detect the mutation site.

The radiography device may further comprise a two-dimensional imagegeneration unit that generates a two-dimensional image of the subject onthe basis of a tomographic image of the subject obtained by thetomosynthesis imaging. The radiography device control unit may performcontrol such that the two-dimensional radiography is not performed andthe two-dimensional image generation unit generates the two-dimensionalimage of the subject in a case in which the part-of-interest detectionunit detects only the mutation site suspected as a tumor mass.

The part-of-interest detection unit may detect a mutation site with afirst size in a predetermined range as the mutation site suspected as acalcification and detect a mutation site with a size greater than thefirst size as the mutation site suspected as a tumor mass.

According to a second aspect of the invention, there is provided, aradiography method that is performed in a radiography device which iscapable of performing tomosynthesis imaging and comprises a radiationemitting unit that is capable of irradiating a subject with radiation ata plurality of different incident angles and a radiographic imagegeneration unit that receives the radiation which has been emitted fromthe radiation emitting unit and passed through the subject and generatesa radiographic image indicating the subject. The method comprises:detecting a mutation site suspected as a lesion from the radiographicimage of the subject which is obtained by irradiating the subject withthe radiation emitted from the radiation emitting unit at apredetermined incident angle; and controlling, on the basis of adetection result, whether to perform each of the tomosynthesis imagingin which the radiographic image generation unit generates a radiographicimage while the radiation emitting unit changes the incident angle ofthe radiation, and two-dimensional radiography in which the radiationemitting unit is fixed to a predetermined incident angle and theradiographic image generation unit generates a radiographic image.

According to the above-mentioned aspect, the radiographic image isgenerated by the radiation emitting unit and the radiographic imagegeneration unit. The mutation site suspect as a lesion is detected fromthe radiographic image of the subject obtained by irradiating thesubject with the radiation emitted from the radiation emitting unit atthe first incident angle.

It is controlled whether or not each of the tomosynthesis imaging inwhich the radiographic image generation unit generates the radiographicimage while the radiation emitting unit changes the incident angle ofthe radiation and the two-dimensional radiography in which the radiationemitting unit is fixed to the predetermined incident angle and theradiographic image generation unit generates the radiographic image isperformed, on the basis of the detection result. Therefore, it ispossible to obtain a more accurate radiographic image while reducing aburden on the subject, as compared to a case in which both tomosynthesisimaging and two-dimensional radiography are always performed.

In addition, control may be performed such that the tomosynthesisimaging is not performed and the two-dimensional radiography isperformed in a case in which only the mutation site suspected as acalcification is detected. Control may be performed such that thetwo-dimensional radiography is not performed and the tomosynthesisimaging is performed in a case in which only the mutation site suspectedas a tumor mass is detected.

In this case, control may be further performed such that both thetomosynthesis imaging and the two-dimensional radiography are performedin a case in which both the mutation site suspected as a calcificationand the mutation site suspected as a tumor mass are detected.

In this case, the radiography device may generate the radiographicimages with at least two types of resolution. Control may be performedsuch that the two-dimensional radiography is performed at a secondresolution higher than a first resolution in a case in which at leastone of the mutation site suspected as a calcification or the mutationsite suspected as a tumor mass is detected from the radiographic imageof the subject with the first resolution which is obtained byirradiating the subject with the radiation at the first incident angle.In this case, control may be further performed such that thetomosynthesis imaging is performed at the second resolution higher thanthe first resolution in a case in which the mutation site suspected as atumor mass is detected.

Control may be performed such that the two-dimensional radiography isnot performed and the tomosynthesis imaging is performed in a case inwhich the mutation site is not detected.

In this case, the radiography device may perform the tomosynthesisimaging in at least two types of incident angle ranges. (a) Control maybe performed such that the two-dimensional radiography is not performedand the tomosynthesis imaging is performed in a first incident anglerange in a case in which the mutation site is not detected. (b) Controlmay be performed such that the tomosynthesis imaging is not performedand the two-dimensional radiography is performed in a case in which onlythe mutation site suspected as a calcification is detected. (c) Controlmay be performed such that the two-dimensional radiography is notperformed and the tomosynthesis imaging is performed in a secondincident angle range wider than the first incident angle range in a casein which only the mutation site suspected as a tumor mass is detected.(d) Control may be performed such that the tomosynthesis imaging isperformed in the second incident angle range and the two-dimensionalradiography is performed in a case in which both the mutation sitesuspected as a calcification and the mutation site suspected as a tumormass are detected.

In this case, (a1) control may be performed such that the tomosynthesisimaging is performed at a first resolution and in the first incidentangle range in a case in which the mutation site is not detected. (b1)Control may be performed such that the two-dimensional radiography isperformed at a second resolution higher than the first resolution in acase in which only the mutation site suspected as a calcification isdetected. (c1) Control may be performed such that the tomosynthesisimaging is performed at the second resolution higher than the firstresolution and in the second incident angle range wider than the firstincident angle range in a case in which only the mutation site suspectedas a tumor mass is detected. (d1) Control may be performed such that thetomosynthesis imaging is performed at the second resolution and in thesecond incident angle range and the two-dimensional radiography isperformed at the second resolution in a case in which both the mutationsite suspected as a calcification and the mutation site suspected as atumor mass are detected.

In addition, control may be performed such that neither thetomosynthesis imaging nor the two-dimensional radiography is performedand imaging is stopped in a case in which the mutation site is notdetected.

The radiography device may further comprise a two-dimensional imagegeneration unit that generates a two-dimensional image of the subject onthe basis of a tomographic image of the subject obtained by thetomosynthesis imaging. Control may be performed such that thetwo-dimensional radiography is not performed and the two-dimensionalimage generation unit generates the two-dimensional image of the subjectin a case in which only the mutation site suspected as a tumor mass isdetected.

A mutation site with a first size in a predetermined range may bedetected as the mutation site suspected as a calcification and amutation site with a size greater than the first size may be detected asthe mutation site suspected as a tumor mass.

According to a third aspect of the invention, there is provided aradiography program that causes a computer to function as theradiography device control unit of the above-mentioned radiographydevice.

According to a fourth aspect of the invention, there is provided anon-transitory storage medium storing a radiography program that causesa computer to function as the radiography device control unit of theabove-mentioned radiography device.

According to the above-mentioned aspects, it is possible to provide aradiography device, a radiography method, a radiography program, and aprogram storage medium which can obtain an accurate radiographic imagewhile reducing a burden on a subject.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view illustrating an example of the structure of aradiography device according to an embodiment.

FIG. 2 is a diagram illustrating an example of the structure of theradiography device according to the embodiment during imaging.

FIG. 3 is a diagram illustrating the operation of the radiography deviceaccording to the embodiment during imaging.

FIG. 4 is a block diagram illustrating an example of the structure of aradiography system according to the embodiment.

FIG. 5 is a diagram illustrating a first example of the structure of aradiation detector.

FIG. 6 is a diagram illustrating a second example of the structure ofthe radiation detector.

FIG. 7A is a diagram illustrating a first example of controlling whetherto perform each of tomosynthesis imaging and 2D imaging on the basis ofthe detection result of a mutation site.

FIG. 7B is a diagram illustrating a second example of controllingwhether to perform each of tomosynthesis imaging and 2D imaging on thebasis of the detection result of a mutation site.

FIG. 8 is a flowchart illustrating an example of the flow of a firstexample of a process performed in a radiography system according to thisembodiment.

FIG. 9 is a flowchart illustrating an example of the flow of a secondexample of the process performed in the radiography system according tothis embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments will be described in detail with reference tothe drawings. The embodiments do not limit the invention.

As illustrated in FIGS. 1 to 3, a radiography device 10 according tothis embodiment captures an image of the breast N of a subject W thatstands up as an object, using radiation (for example, X-rays), and isalso referred to as, for example, a mammography device. In the followingdescription, a front side which is close to the subject W in a case inwhich the subject W faces the radiography device 10 during imaging isreferred to as the front side of the radiography device 10, a back sidewhich is away from the subject W in a case in which the subject W facesthe radiography device 10 is referred to as the rear side of theradiography device 10, and the left-right direction of the subject W ina case in which the subject W faces the radiography device 10 isreferred to as the left-right side of the radiography device 10 (seeeach arrow illustrated in FIGS. 1 and 2).

The imaging target of the radiography device 10 is not limited to thebreast N and may be, for example, another part of the body or an object.The radiography device 10 may be a device which captures an image of thebreast N of the subject W that sits on a chair (including a car seat) ora device which can individually capture images of the left and rightbreasts N of the subject W in a state in which at least the upper partof the body of the subject W stands up.

As illustrated in FIG. 1, the radiography device 10 comprises ameasurement unit 12 which is provided on the front side of the deviceand has a substantially C shape in a side view and a base portion 14which supports the measurement unit 12 from the rear side of the device.

The measurement unit 12 comprises a radiographic stand 22 including aplanar imaging surface 20 which comes into contact with the breast N ofthe subject W that is in a standing state, a compression plate 26 forcompressing the breast N against the imaging surface 20 of theradiographic stand 22, and a holding portion 28 which supports theradiographic stand 22 and the compression plate 26. The compressionplate 26 is made of a member that transmits radiation. A sensor thatdetects the position of the compression plate 26 relative to theradiographic stand 22 (particularly, the imaging surface 20) is providedin the holding portion 28. The radiography device 10 can detect thethickness of the breast using the sensor.

In addition, the measurement unit 12 comprises a radiation emitting unit24 that is provided with a radiation source 30 (see FIG. 4), such as aradiation tube, and emits radiation for examination from the radiationsource 30 to the imaging surface 20 and a support portion 29 that isseparated from the holding portion 28 and supports the radiationemitting unit 24.

Furthermore, the measurement unit 12 is provided with a rotating shaft16. Therefore, the measurement unit 12 can be rotated on the baseportion 14. The rotating shaft 16 is fixed to the support portion 29.The rotating shaft 16 is rotated integrally with the support portion 29.

Gears are provided in the rotating shaft 16 and the holding portion 28and switch between an engaged state and a disengaged state. The holdingportion 28 can switch between a state in which the holding portion 28 isconnected to the rotating shaft 16 and is rotated integrally with therotating shaft 16 and a state in which the holding portion 28 isseparated from the rotating shaft 16 and the rotating shaft 16 rotatesidle.

The switching mechanism is not limited to the gear and various types ofmechanical elements can be used to switch between the transmission andnon-transmission of the torque of the rotating shaft 16.

The holding portion 28 supports the radiographic stand 22 and theradiation emitting unit 24 such that the imaging surface 20 and theradiation emitting unit 24 are spaced at a predetermined distance. Theholding portion 28 also supports the compression plate 26 such that thecompression plate 26 can slide on the holding portion 28. Therefore, thegap between the compression plate 26 and the imaging surface 20 isvariable.

The imaging surface 20 with which the breast N comes into contact ismade of carbon in terms of the transmittance or intensity of radiation.A radiation detector 42 that is irradiated with radiation which haspassed through the breast N and the imaging surface 20 and detects theradiation is provided in the radiographic stand 22. Image informationindicating a radiographic image is generated on the basis of theradiation detected by the radiation detector 42 and a radiographic imageis generated by an image processing unit which will be described below.The generation of the radiographic image will be described in detailbelow.

The radiography device 10 according to this embodiment can irradiate thebreast N with radiation at different incident angles (while changing theincident angle) with respect to a detection surface of the radiationdetector 42 in a predetermined range and can capture the images of thebreast N at different incident angles. Here, the incident angle means anangle formed between a line normal to the detection surface of theradiation detector 42 and a radiation axis. In addition, in thisembodiment, the detection surface of the radiation detector 42 issubstantially parallel to the imaging surface 20.

In the radiography device 10 according to this embodiment, asillustrated in FIGS. 2 and 3, in a case in which the breast N isirradiated with radiation at different incident angles with respect tothe detection surface of the radiation detector 42 in a predeterminedrange (for example, in a range of ±10° or ±20° with respect to the linenormal to the detection surface of the radiation detector 42) to capturethe image of the breast N (hereinafter, in some cases, this imagingprocess is referred to as tomosynthesis imaging and a predeterminedrange of different incident angles during tomosynthesis imaging isreferred to as an incident angle range), the rotating shaft 16 rotatesidle with respect to the holding portion 28 such that the radiographicstand 22 and the compression plate 26 do not move and the supportportion 29 is rotated such that only the radiation emitting unit 24 ismoved in an arc shape. In this embodiment, as illustrated in FIG. 3, theposition of the radiation emitting unit 24 is moved from an angle α at apredetermined angular interval of θ and imaging is performed at npositions, that is, positions P1 to Pn of the radiation emitting unit24. In the following description, the incident angle of radiation in adirection normal to the detection surface of the radiation detector 42is simply referred to as an “incident angle”.

FIGS. 2 and 3 illustrate the posture of the radiography device 10 andthe position of the radiation emitting unit 24 during tomosynthesisimaging, respectively. As illustrated in FIGS. 2 and 3, the supportportion 29 which supports the radiation emitting unit 24 is inclined andthen tomosynthesis imaging is performed. In tomosynthesis imaging,imaging is performed while the incident angle of radiation emitted bythe radiation emitting unit 24 is being changed. The tomosynthesisimaging also includes a case in which the radiation emitting unit 24emits radiation while being moved and a case in which the radiationemitting unit 24 is moved by a predetermined angle θ, is stopped, emits,and starts to move.

In general, in a case in which tomosynthesis imaging is performed, thebreast N of the subject W is irradiated with radiation n times.Therefore, a dose of radiation is reduced such that an exposure dosedoes not increase. For example, radiation is emitted such that the totaldose of radiation during n irradiation operations is equal to thatduring general two-dimensional radiography (general imaging in which thesubject is irradiated with radiation at a fixed position, without movingthe radiation source 30, and then an image of the subject is captured).

The radiography device 10 according to this embodiment can perform bothcranio & caudal (CC) imaging and mediolateral-oblique (MLO) imaging forthe breast N. During the CC imaging, the posture of the holding portion28 is adjusted such that the imaging surface 20 faces the ground in thevertical direction, and the posture of the support portion 29 isadjusted such that the radiation emitting unit 24 is perpendicular tothe normal line to the imaging surface 20 (that is, 0°). Then, theradiation emitting unit 24 emits radiation to the breast N in adirection from the head to the feet of the subject W that is in astanding state and the CC imaging is performed. During the MLO imaging,in general, the posture of the holding portion 28 is adjusted, with theradiographic stand 22 rotated at an angle that is equal to or greaterthan 45° and less than 90°, as compared to the CC imaging, and theholding portion 28 is positioned such that the armpit of the subject Wcomes into contact with a side wall corner portion 22A of theradiographic stand 22 which is on the front side of the device. Then,the radiation emitting unit 24 emits radiation to the breast N in adirection from the center of the body axis of the subject W to theoutside and the MLO imaging is performed.

A chest wall surface 25 with which a chest part below the breast N ofthe subject W comes into contact during imaging is formed on the surfaceof the radiographic stand 22 that is disposed on the front side of thedevice. The chest wall surface 25 has a planar shape.

FIG. 4 illustrates an example of the structure of a radiography system 6according to this embodiment.

The radiography system 6 according to this embodiment comprises theradiography device 10, an image processing device 50, and a displaydevice 80.

The radiography device 10 includes the radiation emitting unit 24, theradiation detector 42, an operation panel 44, a radiography devicecontrol unit 46, and a communication I/F unit 48.

The radiography device control unit 46 according to this embodiment hasa function of controlling the overall operation of the radiographydevice 10 and comprises a central processing unit (CPU), a memoryincluding a read only memory (ROM) and a random access memory (RAM), anda non-volatile storage unit such as a hard disk drive (HDD) or a flashmemory. In this embodiment, the radiography device control unit 46includes an image processing unit 45 and a part-of-interest detectionunit 47. For example, the image processing unit 45 or thepart-of-interest detection unit 47 is partially included in, forexample, the CPU, the ROM, and the HDD. The radiography device controlunit 46 is connected to the radiation emitting unit 24, the radiationdetector 42, the operation panel 44, and the communication I/F unit 48.

When an irradiation instruction is received from the operator through anexposure switch displayed on an instruction input unit 84, theradiography device control unit 46 directs the radiation source 30provided in the radiation emitting unit 24 to emit radiation to theimaging surface 20 according to an imaging menu which is set on thebasis of the designated exposure conditions. In this embodiment, theradiation source 30 emits cone beam radiation (for example, acone-shaped X-ray beam).

A radiographic image generation unit generates a radiographic image ofthe subject on the basis of radiation that has passed through thesubject. In this embodiment, the radiographic image generation unitincludes the radiation detector 42 and the image processing unit 45. Theradiation detector 42 receives radiation which carries imageinformation, records the image information, and outputs the recordedimage information. The radiation detector 42 is, for example, a flatpanel detector (FPD) that includes a radiation sensitive layer andconverts radiation into digital data. The radiation sensitive layer canbe provided substantially in parallel to the imaging surface 20. Whenradiation is emitted, the radiation detector 42 outputs imageinformation indicating a radiographic image to the image processing unit45 in the radiography device control unit 46. In this embodiment, theradiation detector 42 receives the radiation which has passed throughthe breast N and image information indicating a radiographic image isobtained. Then, the image processing unit 45 performs necessaryprocesses, such as a gain correction process, an offset correctionprocess, and a defective pixel correction process, for the imageinformation obtained by the radiation detector 42 to generate aradiographic image. The position of the image processing unit 45 is notlimited to that in this embodiment. For example, the image processingunit 45 may be provided in the radiation detector 42. Alternatively, theimage processing unit 45 may be provided in the image processing device50, which will be described below.

The part-of-interest detection unit 47 detects a mutation site that issuspected as a lesion from the radiographic image generated by the imageprocessing unit 45. Specifically, the part-of-interest detection unit 47detects mutation sites including a mutation site that is suspected as acalcification and a mutation site that is suspected as a tumor mass.More specifically, the part-of-interest detection unit 47 determineswhether the mutation site is a mutation site suspected as acalcification or a mutation site suspected as a tumor mass on the basisof the size of the mutation site. In addition, information (for example,a threshold value indicating a first size in a predetermined range,which will be described below) required for the part-of-interestdetection unit 47 to determine whether the mutation site is a mutationsite suspected as a calcification or a mutation site suspected as atumor mass is stored in, for example, the memory of the radiographydevice control unit 46, which will be described below.

In this embodiment, the image processing unit 45 and thepart-of-interest detection unit 47 are provided as a portion of theradiography device control unit 46 in the radiography device controlunit 46 in order to perform processing at a high speed, without passingthrough a network 49. However, the invention is not limited thereto. Theimage processing unit 45 and the part-of-interest detection unit 47 maybe implemented by hardware different from the radiography device controlunit 46. In a case in which the image processing unit 45 and thepart-of-interest detection unit 47 are implemented by differenthardware, for example, they may be provided in the image processingdevice 50. In a case in which the image processing unit 45 and thepart-of-interest detection unit 47 are provided in the image processingdevice 50, information required for the part-of-interest detection unit47 to detect the mutation site may be stored in, for example, a ROM 54of the image processing device 50. In addition, the image processingunit 45 and the part-of-interest detection unit 47 may be implemented byhardware, or the CPU may execute software, that is, a program, toimplement the image processing unit 45 and the part-of-interestdetection unit 47. In this case, the software may be executed by thesame computer as that executing software for controlling the overalloperation of the imaging device or may be executed by a differentcomputer.

In this embodiment, the radiographic image generation unit can generateradiographic images with different resolutions. Specifically, theradiation detector 42 can generate image information items with aplurality of types of resolutions. More specifically, the radiationdetector 42 can perform a process (so-called binning process) whichcollectively reads information from a plurality of pixels and a processwhich reads information from each pixel. That is, it is possible toobtain image information indicating radiographic images with two typesof resolutions. When the image processing unit 45 performs imageprocessing for the image information, it is possible to finally obtainradiographic images with two types of resolutions. The structure of theradiation detector 42 which can perform the binning process will bedescribed in detail below.

The instruction input unit 84 has a function of setting, for example,various kinds of operation information including imaging conditions andvarious kinds of operation instructions. The operation panel 44 also hasa function which enables a radiologist to move up and down thecompression plate 26 to compress the breast of a subject before imagingor inclines the support portion 29 (that is, radiation emitting unit 24)in order to perform, for example, CC imaging or MLO imaging. Forexample, the operation panel 44 is provided as a plurality of switchesin the radiographic stand 22 of the radiography device 10. The operationpanel 44 may be provided as a touch panel.

The imaging conditions set by the instruction input unit 84 includeexposure conditions including a tube voltage, a tube current, and anirradiation time and information such as posture information. Inaddition, the posture information designated by the instruction inputunit 84 includes information indicating imaging positions (includingincident angles) in a case in which radiation is incident on the breastN at a plurality of incident angles to capture images.

In addition, for example, the exposure conditions, various kinds ofoperation information including the posture information, and variouskinds of operation instructions may be set by the operator through theinstruction input unit 84, may be obtained from other control devices (aradiology information system (RIS) that manages information about, forexample, medical examination and diagnosis using radiation), or may bestored in the storage unit in advance.

When various kinds of information are set through the instruction inputunit 84, the radiography device control unit 46 directs the radiationemitting unit 24 to emit radiation to the part (breast N), of which theimage is to be captured, in the subject W according to the imaging menuwhich is set on the basis of various kinds of set information, therebycapturing a radiographic image. In a case in which tomosynthesis imagingis performed for the breast N, the radiography device control unit 46adjusts the posture of the holding portion 28, with the imaging surface20 up, and adjusts the posture of the support portion 29, with theradiation emitting unit 24 located above the imaging surface 20. Then,as illustrated in FIG. 3, the radiography device control unit 46 rotatesthe support portion 29 on the basis of the imaging conditions such thatthe radiation emitting unit 24 is moved from the angle α at an angularinterval of θ in an arch shape and directs the radiation source 30provided in the radiation emitting unit 24 to emit radiation. In thisway, n radiographic images in which the incident angles of radiation aredifferent from each other are obtained.

The communication I/F unit 48 is a communication interface which has afunction of receiving and transmitting, for example, the capturedradiographic image or various kinds of information between theradiography device 10 and the image processing device 50 through thenetwork 49.

The image processing device 50 has a function (tomographic imagegeneration unit 68) of generating a tomographic image which isreconstructed from the radiographic image acquired from the radiographydevice 10. In addition, the image processing device 50 has a function(not illustrated) of performing image processing for enabling, forexample, a doctor to observe a tomographic image or a projection imagedisplayed on the display device 80. Hereinafter, for example, a person,such as a doctor, who observes the captured radiographic image or thegenerated tomographic image or diagnoses the mutation site is referredto as a user and the radiographic image which is obtained by thedetection of radiation by the radiation detector 42 during tomosynthesisimaging in the radiography device 10 is referred to as a “projectionimage”.

The image processing device 50 comprises a CPU 52, the ROM 54, a RAM 56,an HDD 58, a communication I/F unit 60, an image display instructionunit 62, an instruction receiving unit 64, the tomographic imagegeneration unit 68, a two-dimensional image generation unit 70, and astorage unit 74. These units are connected to each other so as totransmit and receive information through a bus 75 such as a control busor a data bus.

The CPU 52 controls, for example, the overall operation of the imageprocessing device 50. Specifically, the CPU 52 executes a program 55(including a program for performing each of a tomographic imagegeneration process and a process of generating a tomographic image and atwo-dimensional image, which will be described below) stored in the ROM54 to perform control. In this embodiment, the program 55 is stored inadvance. However, the invention is not limited thereto. For example, theprogram 55 may be stored in a recording medium, such as a CD-ROM or aremovable disk, and may be installed from the recording medium to theROM 54, or may be installed from an external device to the ROM 54through a communication line such as the Internet. The RAM 56 ensures awork area when the CPU 52 executes the program 55. The HDD 58 stores andretains various kinds of data. In this embodiment, the tomographic imagegeneration unit 68 is provided as a portion of the image processingdevice 50 in the image processing device 50. However, the invention isnot limited thereto. The tomographic image generation unit 68 may be ahardware component different from the image processing device 50.

The communication I/F unit 60 is a communication interface which has afunction of transmitting and receiving, for example, the capturedradiographic image or various kinds of information between the imageprocessing device 50 and the radiography device 10 through the network49.

The image display instruction unit 62 has a function of instructing adisplay 82 of the display device 80 to display a radiographic image.

The display device 80 according to this embodiment has a function ofdisplaying the captured radiographic image and comprises the display 82on which the radiographic image is displayed and an instruction inputunit 84. The instruction input unit 84 may be, for example, a touchpanel display, a keyboard, or a mouse. The user (for example, a doctor)can input an instruction related to the display of a radiographic imageor the above-mentioned imaging conditions, using the instruction inputunit 84. In addition, the user can input an imaging start instructionusing the instruction input unit 84. The instruction receiving unit 64has a function of receiving the instruction which is input from the userthrough the instruction input unit 84 of the display device 80.

The tomographic image generation unit 68 has a function ofreconstructing a plurality of projection images to generate tomographicimages that are parallel to the imaging surface 20 at a predeterminedslice interval. In this embodiment, the term “parallel” means“substantially parallel” this is a design error.

As described above, in the radiography device 10 according to thisembodiment, the breast N is compressed by the compression plate 26 andis fixed while coming into contact with the imaging surface 20 of theradiographic stand 22. Therefore, in the radiography device 10 accordingto this embodiment, the incident angle of radiation with respect to adirection normal to the detection surface of the radiation detector 42which is parallel to the imaging surface 20 is equal to the incidentangle of radiation with respect to a direction normal to a tomographicplane of the tomographic image of the breast N.

The tomographic image generation unit 68 generates tomographic imagesfrom a plurality of projection images, which have been captured with theradiation emitting unit 24 (radiation source 30) moved to positions P1,P2, P3, . . . , Pn, at a predetermined slice interval. The projectionposition of a region of interest on the radiographic image variesdepending on the incident angle of radiation with respect to the imagingsurface 20. Therefore, the tomographic image generation unit 68 acquiresthe imaging conditions when the radiographic image is captured by theradiography device 10, calculates the amount of movement of the regionof interest in a plurality of radiographic images on the basis of theincident angle of radiation included in the imaging conditions, andreconstructs the tomographic images on the basis of a knownreconstruction method such as a shift-and-add method.

In addition to the shift-and-add method, a known CT reconstructionmethod can be used as the reconstruction method. For example, a filteredback projection (FBP) method which is a representative example of the CTreconstruction method can be used. The FBP method is a reconstructionmethod which considers parallel plane tomographic scanning intomographic imaging as a part of cone beam CT scanning and is anexpanded version of the filtered back projection method. In addition,the iterative reconstruction method disclosed in JP2011-125698A can beused as the reconstruction method. The iterative reconstruction methodis a reconstruction method for CT and can be applied to reconstructionduring tomosynthesis imaging, similarly to the FBP method.

The two-dimensional image generation unit 70 performs a projectionprocess for a stacked image (three-dimensional image), which is obtainedby stacking a plurality of tomographic images generated by thetomographic image generation unit 68, along a predetermined direction orperforms an addition process which adds corresponding pixel values alonga predetermined direction to generate a two-dimensional image.

The two-dimensional image generated by the two-dimensional imagegeneration unit 70 will be described in brief. In mammography diagnosis,tomosynthesis imaging has come into widespread use. However, in manycases, tomographic images obtained by tomosynthesis imaging are used forpositioning as a function of supplementing radiographic images obtainedby the two-dimensional radiography (mammography). The reason for this isthat the radiographic image obtained by general two-dimensionalradiography (mammography) has density that a doctor is accustomed toseeing and is different from that of the tomographic image and thedoctor can check the entire radiographic image at one time.

For this reason, in many cases, both two-dimensional radiography(mammography) and tomosynthesis imaging are performed and diagnosis isperformed using a combination of the radiological image obtained by thetwo-dimensional radiography and the tomographic image obtained by thetomosynthesis imaging.

However, if an image corresponding to the radiographic image obtained bythe general two-dimensional radiography (mammography) can be obtained byonly the tomosynthesis imaging, it is possible to significantly reduce aradiation dose and an imaging time. Therefore, in this embodiment, thetwo-dimensional image generation unit 70 is provided in the imageprocessing device 50 in order to generate a two-dimensional imagecorresponding to the radiographic image captured by two-dimensionalradiography (mammography) from a plurality of tomographic imagesgenerated by tomosynthesis imaging.

Each of the tomographic image generation unit 68 and the two-dimensionalimage generation unit 70 can be implemented by hardware, such as ageneral electronic circuit, an application specific integrated circuit(ASIC), or a field programmable gate array (FPGA).

The storage unit 74 has a function of storing, for example, imageinformation indicating each of the projection image captured by theradiography device 10, the tomographic image generated by thetomographic image generation unit 68, and the two-dimensional imagegenerated by the two-dimensional image generation unit 70 and is alarge-capacity storage device such as a hard disk. In this embodiment,the storage unit 74 also stores the imaging conditions (for example, theincident angle of radiation) when the radiography device 10 captures aradiographic image.

Next, an example of the structure of the radiation detector 42 which canperform the binning process will be described. FIG. 5 is a diagramillustrating a first example of the structure of the radiation detector42.

The radiation detector 42 receives radiation which has passed throughthe subject and outputs image information indicating a radiographicimage of the subject. As illustrated in FIG. 5, the radiation detector42 includes a scintillator (not illustrated) that receives radiation andemits light and a plurality of pixels 21 each of which includes a sensorunit S that receives the light generated by the scintillator andgenerates charge and two switching elements (for example, two thin filmtransistors; hereinafter, simply referred to as transistors) Tr1 and Tr2that read the charge stored in the sensor unit S. In the radiationdetector 42, the plurality of pixels 21 are arranged in a matrix. Inaddition, the radiation detector 42 includes, for example, a chargeamplifier, an A/D converter, and a read control IC which are notillustrated in the drawings. In this embodiment, the radiation detectoris an indirect conversion type in which the scintillator converts lightaccording to radiation, the converted light is emitted to the sensorunit S, and charge is generated. However, the invention is not limitedthereto. A direct-conversion-type radiation detector includes a chargegeneration layer (for example, a layer having Se as a main component)that receives radiation and generates charge and a plurality of pixelseach of which includes two switching elements that read the chargestored in the charge generation layer.

The plurality of pixels 21 are arranged in a matrix in one direction (acontrol line direction corresponding to the lateral direction in FIG. 5;hereinafter, also referred to as a “row direction”) and a direction (asignal line direction corresponding to the longitudinal direction inFIG. 5; hereinafter, also referred to as a “column direction”)intersecting the row direction. In FIG. 5, the arrangement of the pixel21 is illustrated in brief. For example, 1024×1024 pixels 21 arearranged in the row direction and the column direction.

In the radiation detector 42, a plurality of control lines G (G1 to G8in FIG. 5) for controlling the turn-on and turn-off of the transistorsTr1 and a plurality of control lines M (M1 to M4 in FIG. 5) forcontrolling the turn-on and turn-off of the transistors Tr2, and aplurality of signal lines D (D1 to D5 in FIG. 5) which are provided foreach column of the pixels 21 for reading the charge stored in the sensorunits S alternately intersect each other. The charge of each pixel fromthe signal line D is transmitted as digital data (that is, an example ofimage information indicating a radiographic image) to the imageprocessing unit 45 through, for example, a charge amplifier and an A/Dconverter which are not illustrated.

The sensor unit S of each pixel 21 is provided with a semiconductorlayer and a bias electrode that applies a bias voltage to thesemiconductor layer. The bias electrode of each pixel is connected to acommon line (not illustrated). The bias voltage is applied from a powersupply (not illustrated) through the common line.

A control signal for switching (ON/OFF) each transistor Tr1 is suppliedto the control line G. As such, when the control signal is supplied toeach control line G, each transistor Tr1 is switched (ON/OFF). Inaddition, a control signal for switching (ON/OFF) each transistor Tr2 issupplied to the control line M. As such, when the control signal issupplied to each control line M, each transistor Tr2 is switched(ON/OFF).

An electric signal corresponding to the amount of charge stored in eachpixel 21 is supplied to the signal line D through the transistor Tr1 orthe transistor Tr2, according to the switching state (ON/OFF state) ofthe transistor Tr1 and the switching state (ON/OFF state) of thetransistor Tr2 in each pixel 21.

In this embodiment, as illustrated in FIG. 5, in the radiation detector42, the arrangement of the transistor Tr1, the transistor Tr2, and thesensor unit S in the even-numbered control lines G is reverse to thearrangement of the transistor Tr1, the transistor Tr2, and the sensorunit S in the odd-numbered control lines G (in the vertical direction ofFIG. 5).

The radiation detector 42 having the above-mentioned structure canperform imaging at two different types of resolutions. In thisembodiment, the higher of two types of resolutions is referred to ashigh resolution and the lower of two types of resolutions is referred toas low resolution.

That is, in a case in which a high-resolution image is captured, acontrol signal is input to the control lines M such that the transistorsTr2 are turned off and a control signal is sequentially input to thecontrol lines G such that the transistors Tr1 are turned on. In thepixel 21 in which the transistor Tr1 is turned on, charge is read fromthe sensor unit S. The charge of one pixel 21 is sequentially output tothe signal line D.

In a case in which a low-resolution image is captured, a control signalis input to the control line G such that the transistors Tr1 are turnedoff and a control signal is sequentially input to the control line Msuch that each transistor Tr2 is turned on. In the pixel 21 in which thetransistor Tr2 is turned on, charge is read from the sensor unit S.Then, the change is output to the signal line D. Therefore, the chargesof four pixels 21 are collectively output to one signal line D and aresubjected to the subsequent process. Finally, a radiographic imagehaving a lower resolution than that in a case in which the transistorTr2 is turned off and the transistor Tr1 is turned on is obtained.

Next, another example of the structure of the radiation detector 42which can perform the binning process will be described. FIG. 6 is adiagram illustrating a second example of the structure of the radiationdetector 42.

The radiation detector 42 illustrated in FIG. 6 has the same structureas that illustrated in FIG. 5 except that a plurality of pixels 21, eachof which has a hexagonal pixel region, are two-dimensionally arranged ina honeycomb shape while being adjacent to each other and form a regionhaving a substantially rectangular shape as a whole. Each pixel 21includes a sensor unit 103 that receives light generated by thescintillator and generates charge, a charge storage capacitor 5 thatstores the charge generated by the sensor unit 103, and two thin filmtransistors (hereinafter, simply referred to as transistors) 4 a and 4 bthat read the charge stored in the charge storage capacitor 5.

The pixels 21 are arranged in the honeycomb shape as follows. A firstpixel row in which a plurality of pixels 21 that have the same size andhave hexagonal pixel regions are arranged in the row direction (thehorizontal direction in FIG. 6) and a second pixel row in which aplurality of pixels 21 that have the same size as the pixels 21 in thefirst pixel row and have hexagonal pixel regions are arranged in the rowdirection are alternately arranged in a direction intersecting thecolumn direction (the vertical direction in FIG. 6). In addition, thepixels 21 in the second pixel row are arranged between adjacent pixelsin the first pixel row so as to correspond thereto and to be shifted byhalf of the arrangement pitch of the pixels 21 in the first pixel row 21in the row direction.

The radiation detector 42 comprises first control lines G1-0 to G1-7corresponding to each pixel row (the first control lines G1-0 to G1-7are also collectively referred to as first control lines G1. Inaddition, in a case in which control lines including the other controllines, which will be described below, are generically referred, they aresimply referred to as control lines G). The gate electrodes of thetransistors 4 a provided in each pixel 21 are connected to the firstcontrol lines G1. The turn-on and turn-off of the transistors 4 a arecontrolled by signals supplied to the first control lines G1. Inaddition, the radiation detector 42 comprises second control lines G2-0to G2-3 which are arranged so as to correspond to each pixel rowincluding the first control lines G1-0 to G1-3 (the second control linesG2-0 to G2-3 are also collectively referred to as second control linesG2) and third control lines G3-0 to G3-3 which are arranged so as tocorrespond to each pixel row including the first control lines G1-4 toG1-7 (the third control lines G3-0 to G3-3 are also collectivelyreferred to as third control lines G3). The gate electrodes of thetransistors 4 b that are provided in pixels forming a pixel group, whichwill be described below, are connected to the second control lines G2and the third control lines G3. The turn-on and turn-off of thetransistors 4 b are controlled by signals supplied to the second controllines G2 and the third control lines G3.

As such, the radiation detector 42 has a structure in which a pluralityof pixel rows, each of which includes one first control line G1 and onesecond control line G2, and a plurality of pixel rows, each of whichincludes one first control line G1 and one third control line G3, arearranged. In addition, the radiation detector 42 comprises a pluralityof signal lines D1 to D6 (which are collectively referred to as signallines D) for reading charge which is generated in the sensor unit 103 ofeach pixel and is then stored in the charge storage capacitor 5 and aplurality of common (common ground) lines 31. The charge of each pixeltransmitted from the signal line D is converted into digital data (thatis, an example of image information indicating a radiographic image) by,for example, a charge amplifier and an A/D converter (not illustrated)and is then transmitted to the image processing unit 45.

It is also possible to perform imaging at two different types ofresolutions, using the radiation detector 42 illustrated in FIG. 6.Hereinafter, the higher of the two types of resolutions is referred toas high resolution and the lower of the two types of resolutions isreferred to as low resolution.

That is, in a case in which a high-resolution image is captured, acontrol signal for turning off the transistor 4 b of each pixel 21 istransmitted to the second control lines G2-0 to G2-3 and the thirdcontrol lines G3-0 to G3-3. In addition, a control signal issequentially transmitted from the first control lines G1-0 to G1-7 tothe gate of each transistor 4 a in order to turn on the transistor 4 aof each pixel 21. Then, the transistors 4 a of the pixels 21 in eachpixel row are sequentially turned on and charge is read from the sensorunit 103 through the transistor 4 a. The charge of each signaltransmitted from the signal line D is converted into digital data (thatis, an example of image information indicating a radiographic image) by,for example, the charge amplifier and the A/D converter (notillustrated). The digital data of each pixel is transmitted to the imageprocessing unit 45 and is subjected to image processing. Finally, ahigh-resolution radiographic image is obtained.

As such, in the radiation detector 42, a charge signal corresponding toeach pixel 21 in each pixel row is transmitted to each of the signallines D1 to D6 in order to acquire high-resolution image information. Inthis way, it is possible to obtain image information indicating aradiographic image, using radiation that is emitted to the radiationdetector 42.

On the other hand, in a case in which a low-resolution image iscaptured, the second control lines G2 and the third control lines G3 areused. First, the relationship between each pixel and the second andthird control lines G2 and G3 will be described. It is assumed that,among a plurality of pixels 21 illustrated in FIG. 6, for example, fourpixels P0 to P3 form a pixel group PG0, four pixels P4 to P7 form apixel group PG1, four pixels P8 to P11 form a pixel group PG2, fourpixels P12 to P15 form a pixel group PG3, and four pixels P16 to P19form a pixel group PG4. In the five pixel groups, the second controlline G2-0 is connected to the gate electrodes of the transistors 4 b inthe pixel P0 of the pixel group PG0, the pixel P4 of the pixel groupPG1, and the pixel P8 of the pixel group PG2. In addition, the secondcontrol line G2-1 is connected to the gate electrodes of the transistors4 b in the pixels P1 to P3 of the pixel group PG0, the pixels P5 to P7of the pixel group PG1, and the pixels P9 to P11 of the pixel group PG2.

Similarly, the second control line G2-2 is connected to the gateelectrodes of the transistors 4 b in the pixel P12 of the pixel groupPG3 and the pixel P16 of the pixel group PG4 and the second control lineG2-3 is connected to the gate electrodes in the pixels P13 to P15 of thepixel group PG3 and the pixels P17 to P19 of the pixel group PG4. In theradiation detector 42, the connection between the third control linesG3-0 to G3-3 and the pixel groups (PG5 to PG9) including pixels P20 toP23, pixels P24 to P27, pixels P28 to P31, pixel P32 to P35, and pixelsP36 to P39 is the same as the connection between the pixel groups PG0 toPG4 and the second control lines G2-0 to G2-3.

Next, the control of each switching element when a low-resolution imageis captured will be described. In a case in which an instruction tocapture a low-resolution image is input to the radiation detector 42, acontrol signal is transmitted from the first control lines G1-0 to G1-7to the gate electrode of the transistor 4 a in each pixel 21 in order toturn off the transistor 4 a of each pixel 21.

In addition, a control signal for turning on the correspondingtransistors at the same time is transmitted to the second control linesG2-0 to G2-3. As a result, the transistors 4 b of all of the pixels 21in the pixel groups PG0 to PG4 are turned on. Then, the charges storedin the charge storage capacitors 5 of four pixels P0 to P3 in the pixelgroup PG0 are mixed and a composite charge signal is output to thesignal line D2. Similarly, a composite charge signal from four pixelsP12 to P15 in the pixel group PG3 is output to the signal line D3. Acomposite charge signal from four pixels P4 to P7 in the pixel group PG1is output to the signal line D4. A composite charge signal from fourpixels P16 to P19 in the pixel group PG4 is output to the signal lineD5. A composite charge signal from four pixels P8 to P11 in the pixelgroup PG2 is output to the signal line D6.

Then, a control signal for turning on the corresponding transistors atthe same time is transmitted to the third control lines G3-0 to G3-3.Then, the transistors 4 b of all of the pixels 21 in the pixel groupsPG5 to PG9 are turned on. As a result, a composite charge signal fromfour pixels in the pixel group PG5 is output to the signal line D2. Acomposite charge signal from four pixels in the pixel group PG8 isoutput to the signal line D3. A composite charge signal from four pixelsin the pixel group PG6 is output to the signal line D4. A compositecharge signal from four pixels in the pixel group PG9 is output to thesignal line D5. A composite charge signal from four pixels in the pixelgroup PG7 is output to the signal line D6.

As such, in a case in which a low-resolution image is captured, for eachof a plurality of pixel groups, each of which includes fourpredetermined pixels among a plurality of pixels 21 forming theradiation detector 42, charges stored in the four pixels are combined(subjected to the binning process) and the charge subjected to thebinning process is output to the signal line. This means that, inlow-resolution imaging, 2×2 pixel binning is performed in the radiationdetector 42 to acquire image information at a speed that is four timeshigher than that in high-resolution imaging.

In the examples of the structure illustrated in FIGS. 5 and 6, one pixelcomprises a plurality of transistors and the reading of charge switchesbetween a mode in which change is read from each pixel and a mode inwhich charge is collectively read from a plurality of pixels (binningprocess) to read charge at different resolutions. However, theacquisition of the image information (or radiographic images) withdifferent resolutions is not limited to the above-mentioned example. Forexample, as another example, there is a method in which the radiationdetector 42 has an internal memory and 2×2 pixel binning is performedusing the internal memory. That is, the image information of all of thepixels is read to the internal memory once. In the case ofhigh-resolution imaging, the image information (digital data) of eachpixel is transmitted to the image processing unit 45 without any change.In the case of low-resolution imaging, an operation of adding 2×2 pixelinformation (digital data) is performed using the internal memory andthe pixel information is transmitted to the image processing unit 45. Inthis case, the radiation detector 42 has a structure in which oneswitching element is provided in each pixel, which is sufficient toachieve low-resolution imaging. In addition, in the case oflow-resolution imaging, instead of performing the binning process usingthe internal memory of the radiation detector 42, a thinning-out processmay be performed. In a case in which the thinning-out process isperformed in the radiation detector 42, the following methods are used:a method which reads information from only some of a plurality ofpixels; and a method which reads information from all of the pixels andoutputs information of only one pixel in a unit of 2 pixels×2 pixelsfrom the internal memory of the radiation detector 42 to the imageprocessing unit 45. In addition, the addition (binning process) of thepixel information or the thinning-out process may be performed in theimage processing unit 45. That is, the radiographic image generationunit needs to have at least a function of generating radiographic imageswith different resolutions.

In this embodiment, tomosynthesis imaging and general mammography(two-dimensional radiography; hereinafter, also referred to as 2Dimaging) can be performed. However, it is not necessary to constantlyperform the two imaging methods. In some cases, only one of the twoimaging methods may be performed. In this embodiment, a pre-irradiationprocess for determining, for example, irradiation conditions isperformed. A radiographic image (hereinafter, referred to as apre-irradiation image) obtained by the pre-irradiation process isanalyzed to control whether to perform each of tomosynthesis imaging and2D imaging.

Specifically, in this embodiment, the part-of-interest detection unit 47of the radiography device control unit 46 detects a mutation site whichis suspected as a lesion from the pre-irradiation image, using ananalysis technique such as computer aided diagnosis (CAD). Then, theradiography device control unit 46 controls whether to perform each oftomosynthesis imaging and 2D imaging on the basis of the detectionresult.

In addition, the part-of-interest detection unit 47 has the capabilityto determine whether the detected mutation site is a mutation sitesuspected as a calcification or a mutation site suspected as a tumormass. In particular, in this embodiment, the part-of-interest detectionunit 47 can detect whether the detected mutation site is a mutation sitesuspected as a calcification or a mutation site suspected as a tumormass, on the basis of the size of the detected mutation site.Specifically, the part-of-interest detection unit 47 has a radiographicimage analysis function, such as CAD, and can detect the candidates ofan abnormal shadow as the mutation site from the radiographic image. Inaddition, the part-of-interest detection unit 47 includes a sizedetection unit that detects the size of the mutation site. For example,the size detection unit detects the maximum diameter of a circle that iscircumscribed about the mutation site as the size of the mutation site.In a case in which the size of the mutation site detected by the sizedetection unit is a first size (for example, equal to or greater thanseveral pixels and equal to or less than 10 pixels) in a predeterminedrange, the part-of-interest detection unit 47 detects the mutation siteas a mutation site that is suspected as a calcification. In a case inwhich the size of the mutation site is greater than the first size (forexample, greater than 10 pixels), the part-of-interest detection unit 47detects the mutation site as a mutation site that is suspected as atumor mass. In other words, the part-of-interest detection unit 47 candetect, as the mutation site, a part having a size that is equal to orgreater than the first size (for example, equal to or greater thanseveral pixels) in the predetermined range. The “first size in apredetermined range” and the “size greater than the first size”, and the“size equal to or greater than the first size in a predetermined range”will be described in detail below. The “first size in a predeterminedrange” indicates a limited range having an upper limit and a lowerlimit. When a pixel is used as a unit, the “first size in apredetermined range” indicates, for example, a range from several pixelsto 10 pixels. When a meter is used as a unit, the “first size in apredetermined range” indicates a range from 100 μm to 1 mm. The “sizegreater than the first size” means that at least a lower limit is setand the size is greater than the lower limit. The lower limit is anupper limit designated by the “first size in a predetermined range”. Forexample, when the upper limit of the “first size in a predeterminedrange” is 10 pixels, the “size greater than the first size” means thatthe size is greater than 10 pixels. In addition, the “size greater thanthe first size” may indicate a range from 10 pixels to 1000 pixels. Thatis, when the range of the “size greater than the first size” is set, theupper limit of the range may or may not be set. Finally, the “size equalto or greater than the first size in a predetermined range” is a roughrange satisfying the “first size in a predetermined range” and the “sizegreater than the first size”. Specifically, the “size equal to orgreater than the first size in a predetermined range” means that atleast a lower limit is set and the size is greater than the lower limit.The lower limit is a lower limit designated by the “first size in apredetermined range”. For example, when the lower limit set by the“first size in a predetermined range” is several pixels, the “size equalto or greater than the first size in a predetermined range” means thatthe size is equal to or greater than several pixels. The range of themutation site having the same size as a boundary value of the upperlimit or the lower limit is not limited to the above description. Inthis embodiment, the size detected by the size detection unit is themaximum diameter which is a one-dimensional length. However, theinvention is not limited thereto. The size may be a two-dimensional sizesuch as the number of pixels or an area. In this case, the number ofpixels or an area is used as the boundary value.

As such, since the part-of-interest detection unit 47 detects whetherthe mutation site is a mutation site suspected as a calcification or amutation site suspected as a tumor mass on the basis of the size of themutation site, it is easy to appropriately select the resolution of atomographic image in a depth direction and the resolution of atwo-dimensional image and to perform imaging, which will be describedbelow.

The radiography device control unit 46 (part-of-interest detection unit47) detects the mutation site, using, for example, the techniquedisclosed in JP2011-120747A. When the candidates of an abnormal shadow(mutation site) in the breast are detected on the basis of the capturedradiographic image, it is possible to detect the candidates of theabnormal shadow (mutation site), using a method using an iris filteringprocess (also see JP1998-97624A (JP-H10-97624A)) or a method using amorphological filter (also see JP1996-294479A (JP-H08-294479A)), asdescribed in JP2011-120747A.

In this embodiment, the radiography device 10 can generate radiographicimages with two types of resolutions and can move the radiation emittingunit 24 in two types of incident angle ranges. These functions are usedin tomosynthesis imaging, pre-irradiation, and 2D imaging. Hereinafter,the higher of the two types of resolutions is referred to as highresolution and the lower of the two types of resolutions is referred toas low resolution. In addition, the narrower of the two types ofincident angle ranges is referred to as a narrow incident angle rangeand the wider of the two types of incident angle ranges is referred toas a wide incident angle range. For example, values, such as theincident angle range, a first incident angle, and a predeterminedincident angle, which will be described below, are stored in the memoryof the radiography device control unit 46 in advance.

In this embodiment, the radiography device control unit 46 controlswhether to perform each of tomosynthesis imaging and 2D imaging and theissue of an instruction to generate a two-dimensional image, on thebasis of the detection result of the mutation site suspected as a lesionby the radiography device control unit 46 (part-of-interest detectionunit 47). For example, control can be performed as illustrated in FIGS.7A and 7B.

In FIG. 7A, in a case in which a mutation site suspected as a lesion isnot detected by image analysis, such as CAD, for the pre-irradiationimage, tomosynthesis imaging is performed at low resolution and in anarrow incident angle range and 2D imaging is not performed or aninquiry about whether 2D imaging is required is given to the user suchthat the user selects whether to perform 2D imaging. The display of theinquiry and the selection of the imaging method by the user areperformed through the display device 80. For the setting of notperforming 2D imaging/giving the inquiry, the radiography device controlunit 46 sets one of them in advance. However, the user may change thesettings through the display device 80. In addition, in a case in whicha mutation site suspected as a calcification is detected, tomosynthesisimaging is not performed and only high-resolution 2D imaging isperformed since the mutation site suspected as a calcification is small.In a case in which a mutation site suspected as a tumor mass isdetected, tomosynthesis imaging is performed at high resolution and in awide incident angle range and 2D imaging is not performed and ends, orthe two-dimensional image generation unit 70 generates a two-dimensionalimage on the basis of a tomographic image. In a case in which both themutation site suspected as a calcification and the mutation sitesuspected as a tumor mass are detected, tomosynthesis imaging isperformed at high resolution and in a wide incident angle range and 2Dimaging is performed at high resolution. In this case, for the settingof not performing 2D imaging/the generation of a two-dimensional image,the radiography device control unit 46 sets one of them in advance.However, the user may change the settings through the display device 80.

In FIG. 7A, in addition to whether to perform each of tomosynthesisimaging and 2D imaging, imaging conditions, such as resolution and anincident angle range, in tomosynthesis imaging are set in detail on thebasis of the detection result of the mutation site. However, theinvention is not limited thereto. For example, as illustrated in FIG.7B, only whether each of tomosynthesis imaging and 2D imaging isperformed may be controlled. In this case, for imaging conditions, eachimaging process is performed using the settings of the resolution andthe incident angle range stored in the radiography device control unit46 in advance.

That is, in FIG. 7B, in a case in which a mutation site suspected as alesion is not detected by image analysis, such as CAD, for thepre-irradiation image, tomosynthesis imaging and 2D imaging are notperformed and are stopped. In a case in which a mutation site suspectedas a calcification is detected, tomosynthesis imaging is not performedand only 2D imaging is performed since the mutation site suspected as acalcification is small. In a case in which a mutation site suspected asa tumor mass is detected, tomosynthesis imaging is performed and 2Dimaging is not performed or the two-dimensional image generation unit 70generates a two-dimensional image without performing imaging. In thiscase, for the setting of not performing 2D imaging/the generation of thetwo-dimensional image, the radiography device control unit 46 sets oneof them in advance. However, the user may change the settings throughthe display device 80. In a case in which both the mutation sitesuspected as a calcification and the mutation site suspected as a tumormass are detected, both tomosynthesis imaging and 2D imaging areperformed.

As such, in FIG. 7A and FIG. 7B, the radiography device control unit 46controls whether to perform each of tomosynthesis imaging and 2D imagingfor each type of mutation site suspected as a lesion, on the basis ofthe detection result of the mutation site.

In this embodiment, the part-of-interest detection unit 47 of theradiography device control unit 46 detects the mutation site suspectedas a lesion. However, for example, in a case in which thepart-of-interest detection unit 47 has low processing capability, thefunctions of the part-of-interest detection unit 47 may be provided inthe image processing device 50. In this embodiment, among the imagingconditions when tomosynthesis imaging or 2D imaging is performed, forexample, exposure conditions may be determined as follows. That is, theradiography device control unit 46 analyzes the shade of theradiographic image obtained by pre-irradiation. Then, an irradiationdose in tomosynthesis imaging and an irradiation dose in 2D imaging maybe determined such that the shade of the radiographic image (projectionimage) obtained by tomosynthesis imaging or 2D imaging falls within apredetermined range. In 2D imaging, similarly to general mammography,the radiation emitting unit 24 is fixed to a predetermined incidentangle (the vertical direction in FIG. 2) and imaging is performed underthe imaging conditions determined by the pre-irradiation to generate aradiographic image of the breast. In other words, in tomosynthesisimaging, the radiation emitting unit 24 emits radiation while beingmoved in the incident angle range and imaging is performed. In 2Dimaging, the radiation emitting unit 24 emits radiation while beingfixed to a predetermined incident angle and imaging is performed.

Next, the operation (radiography method) of the radiography system 6having the above-mentioned structure in the examples illustrated inFIGS. 7A and 7B will be described.

First, the operation of the radiography system 6 in a first exampleillustrated in FIG. 7A will be described. FIG. 8 is a flowchartillustrating an example of the flow (radiography method) of the processof the first example performed in the radiography system 6 according tothis embodiment.

The user brings the breast N of the subject W into contact with theimaging surface 20 of the radiography device 10. In this state, when theuser inputs an operation instruction to start compression, theradiography device 10 moves the compression plate 26 to the imagingsurface 20 so as to compress the breast N in Step 100.

Then, in Step 102, pre-irradiation is performed. After thepre-irradiation, the process proceeds to Step 104. The pre-irradiationis performed, with the radiation emitting unit 24 being inclined at afirst predetermined incident angle with respect to the breast N.Specifically, with the radiation emitting unit 24 being verticallylocated with respect to the radiographic stand 22 (a central position inFIG. 2), the image of the breast N is captured with a radiation dosewhich has been determined on the basis of the thickness of the breast Ndetected by the radiography device 10. In general, when the thickness ofthe breast N is large, the amount of radiation which reaches theradiation detector 42 (passes through the breast N) is reduced.Therefore, in this embodiment, a correspondence relationship among thefirst incident angle, the thickness of the breast N, and a radiationdose is stored in the memory of the radiography device control unit 46in advance. In this embodiment, the radiation detector 42 outputshigh-resolution image information, without performing the binningprocess. However, the radiation detector 42 may perform the binningprocess and output low-resolution image information, in order to reducethe time required to detect a mutation site, which will be describedbelow. Then, the image processing unit 45 performs necessary processes,such as a gain correction process, an offset correction process, and adefective pixel correction process, for the image information of thebreast N obtained by the radiation detector 42 to generate aradiographic image of the breast N (for example, a RAW format is appliedas the format of the image). In addition, the conditions oftomosynthesis imaging or 2D imaging to be performed in the subsequentstep are determined on the basis of the radiographic image obtained bythe pre-irradiation, which will be described below.

In Step 104, the part-of-interest detection unit 47 of the radiographydevice control unit 46 analyzes the radiographic image generated by theimage processing unit 45. The part-of-interest detection unit 47 detectsa mutation site that is suspected as a lesion. Then, the processproceeds to Step 106.

In Step 106, the radiography device control unit 46 (part-of-interestdetection unit 47) determines whether a mutation site suspected as alesion has been detected. Specifically, the radiography device controlunit 46 (the part-of-interest detection unit 47, particularly, the sizedetection unit) determines whether a mutation site with a size that isequal to or greater than the first size in the predetermined range hasbeen detected. In a case in which the determination result is “No”, theprocess proceeds to Step 108. In a case in which the determinationresult is “Yes”, the process proceeds to Step 114.

In Step 108, the radiography device control unit 46 performs controlsuch that low resolution and a narrow incident angle range are set asthe conditions of tomosynthesis imaging. After tomosynthesis imaging isperformed, the process proceeds to Step 110. Specifically, theradiography device control unit 46 performs control such that theradiation detector 42 performs the binning process and the incidentangle range during the acquisition of the projection image of the breastis set to a narrow incident angle range. Tomosynthesis imaging isperformed while the radiation emitting unit 24 (radiation source 30) ismoved in the narrow incident angle range. The tomosynthesis imaging isperformed while the support portion 29 is moved at an angular intervalof, for example, 1° and the radiation detector 42 generates a pluralityof image information items corresponding to the narrow incident anglerange. The image processing unit 45 performs necessary processes, suchas a gain correction process, an offset correction process, and adefective pixel correction process, for the image information obtainedby the radiation detector 42 to generate a radiographic image(projection image) with, for example, a RAW format. Then, the generatedradiographic image is transmitted to the image processing device 50. Thetomographic image generation unit 68 performs image processing, such asFBP, for the radiographic image to generate a tomographic image. Afterthe tomosynthesis imaging, the process proceeds to Step 110, with thecompression plate compressing the breast.

In Step 110, the radiography device control unit 46 determines whetheran inquiry about 2D imaging has been set. Specifically, for example, ina case in which the radiography device control unit 46 sets in advancean inquiry about whether 2D imaging is performed in a case in which nomutation site is detected, that is, the determination result is “Yes”,the process proceeds to Step 112. In a case in which not performing 2Dimaging is set in advance, that is, the determination result is “No”,the fixation of the breast by the compression plate 26 is released and aseries of processes ends. The user changes the setting of not performing2D imaging/giving the inquiry through the display device 80.

In Step 112, the radiography device control unit 46 performs controlsuch that an inquiry about whether 2D imaging is performed is given tothe user through the display device 80. In a case in which the userinputs an instruction to perform 2D imaging through the instructioninput unit 84 of the display device 80, the radiography device controlunit 46 performs control such that 2D imaging is performed and a seriesof processes ends. In a case in which the user inputs an instruction notto perform 2D imaging through the instruction input unit 84 of thedisplay device 80, the radiography device control unit 46 performscontrol such that 2D imaging is not performed and a series of processesend. When a series of processes ends, the fixation of the breast by thecompression plate 26 is released. For example, the compression plate 26is moved in a direction in which it becomes further away from theimaging surface 20 to release the fixation of the breast. In 2D imaging,specifically, the radiation emitting unit 24 is vertically located withrespect to the radiographic stand 22 (a central position in FIG. 2) andemits radiation and the radiation detector 42 obtains image information.At that time, for example, in a case in which high-resolution imageinformation is obtained, the radiation detector 42 does not perform thebinning process and acquires two-dimensional image information with highresolution. Then, the image processing unit 45 performs necessaryprocesses, such as a gain correction process, an offset correctionprocess, and a defective pixel correction process, for the imageinformation to generate a high-resolution radiographic image. Inaddition, the process of inquiring whether resolution is set to lowresolution or high resolution in 2D imaging may be performed at the sametime as the process of inquiring whether to perform 2D imaging. Forexample, in a case in which the user inputs an instruction to performlow-resolution 2D imaging through the instruction input unit 84 of thedisplay device, the radiography device control unit 46 performs controlsuch that 2D imaging is performed and the radiation detector 42 performsthe binning process.

In Step 114, the radiography device control unit 46 (part-of-interestdetection unit 47) determines whether only a mutation site suspected asa calcification has been detected. Specifically, in a case in which thesize of the mutation site detected by the part-of-interest detectionunit 47 of the radiography device control unit 46 is equal to the firstsize in the predetermined range, it is determined that the mutation siteis suspected as a calcification. In a case in which only a mutation sitesuspected as a calcification has been detected, that is, thedetermination result is “Yes”, the process proceeds to Step 116. In acase in which the determination result is “No”, the process proceeds toStep 118.

In Step 116, the radiography device control unit 46 performs controlsuch that 2D imaging is performed and a series of processes ends. Thatis, since the size of the mutation suspected as a calcification issmall, tomosynthesis imaging is not performed and only 2D imaging isperformed. In 2D imaging, the binning process is not performed. That is,a high-resolution radiographic image is generated. After 2D imaging, thefixation of the breast by the compression plate 26 is released. Forexample, the compression plate 26 is moved in a direction in which itbecomes further away from the imaging surface 20 to release the fixationof the breast.

In Step 118, the radiography device control unit 46 (part-of-interestdetection unit 47) determines whether only the mutation site suspectedas a tumor mass has been detected. Specifically, in a case in which thesize of the mutation site detected by the part-of-interest detectionunit 47 of the radiography device control unit 46 is greater than thefirst size in the predetermined range, it is determined that themutation site is suspected as a tumor mass. In a case in which only themutation site suspected as a tumor mass has been detected, that is, thedetermination result is “Yes”, the process proceeds to Step 120. In acase in which the determination result is “No”, in this embodiment, itis determined that both the mutation site suspected as a calcificationand the mutation site suspected as a tumor mass have been detected.Then, the process proceeds to Step 122.

In Step 120, the radiography device control unit 46 performs controlsuch that tomosynthesis imaging is performed at high resolution and in awide incident angle range. That is, the radiography device control unit46 performs control such that the radiation detector 42 does not performthe binning process and the radiation emitting unit 24 (radiationsource) emits radiation while being moved in the wide incident anglerange in the acquisition of the projection image of the breast toperform tomosynthesis imaging. Then, after tomosynthesis imaging iscompleted, the fixation of the breast by the compression plate 26 isreleased. For example, the compression plate 26 is moved in a directionin which it becomes further away from the imaging surface 20 to releasethe fixation of the breast. The tomosynthesis imaging is performed whilethe support portion 29 is moved at an angular interval of, for example,1° and the radiation detector 42 generates a plurality of imageinformation items corresponding to the wide incident angle range. Theimage processing unit 45 performs necessary processes, such as a gaincorrection process, an offset correction process, and a defective pixelcorrection process, for the image information obtained by the radiationdetector 42 to generate a radiographic image (projection image) with,for example, a RAW format. Then, the generated radiographic image istransmitted to the image processing device 50. The tomographic imagegeneration unit 68 performs image processing, such as FBP, for theradiographic image to generate a tomographic image. As such, in a casein which only the tumor mass has been detected, it is not necessary toperform 2D imaging and only tomosynthesis imaging is performed since thesize of the tumor mass is relatively large. Therefore, it is possible toreduce a burden on the subject W caused by the compression of the breastN and to obtain necessary radiographic images (projection images andtomographic images). After tomosynthesis imaging is performed, theprocess proceeds to Step 115.

In Step 115, the radiography device control unit 46 determines whetherthe generation of a two-dimensional image is set. Specifically, forexample, in a case in which the radiography device control unit 46 setsthe two-dimensional image generation unit 70 to generate atwo-dimensional image from the tomographic image obtained bytomosynthesis imaging in advance, that is, the determination result is“Yes”, the process proceeds to Step 117. In a case in which thegeneration of a two-dimensional image is not set in advance, that is,the determination result is “No”, a series of processes ends. As such,it is possible to selectively generate a two-dimensional image, insteadof performing 2D imaging. In addition, the radiography device controlunit 46 sets whether to generate a two-dimensional image or not inadvance. However, the user may change the settings through the displaydevice 80.

In Step 117, the two-dimensional image generation unit 70 generates atwo-dimensional image and a series of processes ends.

In Step 122, the radiography device control unit 46 performs controlsuch that tomosynthesis imaging is performed at high resolution and in awide incident angle range. That is, similarly to Step 120, theradiography device control unit 46 performs control such that theradiation detector 42 does not perform the binning process andtomosynthesis imaging is performed while the radiation emitting unit 24(radiation source 30) is moved in the wide incident angle range in theacquisition of the projection image of the breast. After tomosynthesisimaging is completed, the process proceeds to Step 124, with the breastbeing compressed.

In Step 124, the radiography device control unit 46 performs controlsuch that 2D imaging is performed and a series of processes ends. After2D imaging is completed, the fixation of the breast by the compressionplate 26 is released. For example, the compression plate 26 is moved ina direction in which it becomes further away from the imaging surface 20to release the fixation of the breast. In 2D imaging, for example,similarly to Step 116, the binning process is not performed, imaging isperformed at high resolution, and the image processing unit 45 performsnecessary processes, such as a gain correction process, an offsetcorrection process, and a defective pixel correction process, for theimage information obtained by the radiation detector 42 to generate aradiographic image. That is, in a case in which a calcification and atumor mass have been detected, tomosynthesis imaging and 2D imaging areperformed at high resolution and in a wide incident angle range toobtain necessary radiographic images (projection images and tomographicimages).

As such, in the process according to this example, a mutation sitesuspected as a lesion is detected on the basis of a pre-irradiationimage and whether to perform each of tomosynthesis imaging and 2Dimaging is controlled on the basis of the detection result. Therefore,it is possible to obtain a more accurate radiographic image whilereducing a burden on the subject, as compared to a case in which bothtomosynthesis imaging and 2D imaging are always performed. Inparticular, the effect of the process according to this example will bedescribed in detail. In a case in which a mutation site has not beendetected, it is not necessary to newly perform 2D imaging since thetwo-dimensional image of the breast has already been obtained bypre-irradiation. Tomosynthesis imaging may be performed at lowresolution and in a narrow incident angle range. Therefore, it ispossible to provide an accurate radiographic image while reducing aburden on the subject. In a case in which only the mutation sitesuspected as a calcification has been detected, only 2D imaging isperformed at high resolution since it is necessary to observe theposition and shape of the calcification in detail. In a case in whichonly the mutation site suspected as a tumor mass has been detected,tomosynthesis imaging is performed at high resolution and in a wideincident angle range since it is necessary to observe thethree-dimensional structure of the tumor mass. Since high-resolutionprojection images and tomographic images are acquired by tomosynthesisimaging, it is not necessary to perform 2D imaging. Instead of theabove, when two-dimensional image generation (combination) is performed,it is possible to provide an accurate radiographic image while reducinga burden on the subject. In a case in which both the mutation sitesuspected as a calcification and the mutation site suspected as a tumormass have been detected, it is necessary to observe both thecalcification and the tumor mass in detail. Therefore, tomosynthesisimaging is performed at high resolution and in a wide incident anglerange and 2D imaging is performed at high resolution. As a result, it ispossible to obtain sufficient data for the subsequent detailedexamination.

As an example derived from the process according to this example,control may be performed such that Step 110 and Step 112 are omittedafter Step 108 and 2D imaging is not performed. As another examplederived from the process according to this example, control may beperformed such that Step 117 is provided after Step 108, instead ofomitting Step 110 and Step 112, and a two-dimensional image isautomatically generated, or control may be performed such that Steps 115and 117 are provided and a two-dimensional image is generated accordingto settings.

As still another example derived from the process according to thisexample, control may be performed such that Step 115 and Step 117 areomitted after Step 120 and a two-dimensional image is not generated. Inaddition, as yet another example derived from the process according tothis example, control may be performed such that only Step 115 isomitted after Step 120 and a two-dimensional image is automaticallygenerated.

Next, still yet another example derived from the process according tothis example will be described. In a case in which a mutation site hasnot been detected, tomosynthesis imaging is performed in a narrowincident angle range and 2D imaging is not performed or inquiry aboutwhether 2D imaging is performed is given to the user such that the userselects whether to perform 2D imaging. In a case in which only themutation site suspected as a calcification has been detected,tomosynthesis imaging is not performed and only 2D imaging is performed.In a case in which only the mutation site suspected as a tumor mass hasbeen detected, tomosynthesis imaging is performed in a wide incidentangle range and 2D imaging is not performed or a two-dimensional imageis generated. Then, in a case in which both the mutation site suspectedas a calcification and the mutation site suspected as a tumor mass havebeen detected, tomosynthesis imaging is performed in a wide incidentangle range and 2D imaging is performed. This derivation examplecorresponds to an example in which resolution conditions are omittedfrom FIG. 7A. This derivation example can be applied to a radiographydevice (particularly, a mammography device using a radiation detectorthat does not perform the binning process) which can performtomosynthesis imaging and in which a two-dimensional image/radiographicimage generation unit generates radiographic images at a singleresolution.

The radiography device control unit 46 performs control on the basis ofeach of the above-mentioned derivation examples and the other componentsoperate on the basis of this example.

Next, the operation of the radiography system 6 will be described, usingthe case illustrated in FIG. 7B as a second example. FIG. 9 is aflowchart illustrating an example of the flow (radiography method) ofthe process of the second example performed by the radiography system 6according to this embodiment. In the second example, the same steps asthose in the first example are denoted by the same reference numerals.In this embodiment, radiography device control unit 46 is set in advancesuch that the radiation detector 42 does not perform the binning processand the radiographic image generation unit generates high-resolutionradiographic images (projection images and two-dimensional images).

The user brings the breast N of the subject W into contact with theimaging surface 20 of the radiography device 10. In this state, when theuser inputs an operation instruction to start compression, theradiography device 10 moves the compression plate 26 to the imagingsurface 20 so as to compress the breast N in Step 100.

Then, in Step 102, pre-irradiation is performed. After thepre-irradiation, the process proceeds to Step 104. The pre-irradiationis performed, with the radiation emitting unit 24 being inclined at afirst predetermined incident angle with respect to the breast N.Specifically, with the radiation emitting unit 24 being verticallylocated with respect to the radiographic stand 22 (a central position inFIG. 2), the image of the breast N is captured with a radiation dosewhich has been determined on the basis of the thickness of the breast Ndetected by the radiography device 10. In general, when the thickness ofthe breast N is large, the amount of radiation which reaches theradiation detector 42 (passes through the breast N) is reduced.Therefore, in this embodiment, a correspondence relationship among thefirst incident angle, the thickness of the breast N, and a radiationdose is stored in the memory of the radiography device control unit 46in advance. The image processing unit 45 performs necessary processes,such as a gain correction process, an offset correction process, and adefective pixel correction process, for the image information of thebreast N obtained by the radiation detector 42 to generate aradiographic image of the breast N (for example, a RAW format is appliedas the format of the image). In addition, the conditions oftomosynthesis imaging or 2D imaging to be performed in the subsequentstep are determined on the basis of the radiographic image obtained bythe pre-irradiation, which will be described below.

In Step 104, the part-of-interest detection unit 47 of the radiographydevice control unit 46 analyzes the radiographic image generated by theimage processing unit 45. The part-of-interest detection unit 47 detectsa mutation site that is suspected as a lesion. Then, the processproceeds to Step 106.

In Step 106, the radiography device control unit 46 (part-of-interestdetection unit 47) determines whether a mutation site suspected as alesion has been detected. Specifically, the radiography device controlunit 46 (the part-of-interest detection unit 47, particularly, the sizedetection unit) determines whether a mutation site with a size that isequal to or greater than the first size in the predetermined range hasbeen detected. In a case in which the determination result is “Yes”, theprocess proceeds to Step 114. In a case in which the determinationresult is “No”, a series of processes ends, and the fixation of thebreast by the compression plate 26 is released. For example, thecompression plate 26 is moved in a direction in which it becomes furtheraway from the imaging surface 20 to release the fixation of the breast.

In Step 114, the radiography device control unit 46 (part-of-interestdetection unit 47) determines whether only the mutation site suspectedas a calcification has been detected. Specifically, in a case in whichthe size of the mutation site detected by the part-of-interest detectionunit 47 of the radiography device control unit 46 is equal to the firstsize in the predetermined range, it is determined that the mutation siteis suspected as a calcification. In a case in which only the mutationsite suspected as a calcification has been detected, that is, thedetermination result is “Yes”, the process proceeds to Step 116. In acase in which the determination result is “No”, the process proceeds toStep 118.

In Step 116, the radiography device control unit 46 performs controlsuch that 2D imaging is performed and a series of processes ends. Thatis, since the size of the mutation suspected as a calcification issmall, tomosynthesis imaging is not performed and only 2D imaging isperformed. In the 2D imaging, specifically, the radiation emitting unit24 is vertically located with respect to the radiographic stand 22 (acentral position in FIG. 2) and emits radiation and the radiationdetector 42 obtains image information. The radiation detector 42generates high-resolution image information, without performing thebinning process, and the image processing unit 45 performs necessaryprocesses, such as a gain correction process, an offset correctionprocess, and a defective pixel correction process, to generate aradiographic image. After 2D imaging, the fixation of the breast by thecompression plate 26 is released. For example, the compression plate 26is moved in a direction in which it becomes further away from theimaging surface 20 to release the fixation of the breast.

In Step 118, the radiography device control unit 46 (part-of-interestdetection unit 47) determines whether only the mutation site suspectedas a tumor mass has been detected. Specifically, in a case in which thesize of the mutation site detected by the part-of-interest detectionunit 47 of the radiography device control unit 46 is greater than thefirst size in the predetermined range, it is determined that themutation site is suspected as a tumor mass. In a case in which only themutation site suspected as a tumor mass has been detected, that is, thedetermination result is “Yes”, the process proceeds to Step 119. In acase in which the determination result is “No”, in this embodiment, itis determined that both the mutation site suspected as a calcificationand the mutation site suspected as a tumor mass have been detected.Then, the process proceeds to Step 121.

In Step 119, the radiography device control unit 46 performs controlsuch that tomosynthesis imaging is performed and a series of processesends. That is, tomosynthesis imaging is performed while the radiationemitting unit 24 (radiation source 30) is moved in a predeterminedincident angle range (for example, a wide incident angle range). Then,after tomosynthesis imaging is completed, the fixation of the breast bythe compression plate 26 is released. For example, the compression plate26 is moved in a direction in which it becomes further away from theimaging surface 20 to release the fixation of the breast. Thetomosynthesis imaging is performed while the support portion 29 is movedat an angular interval of, for example, 1° to generate a plurality ofradiographic images corresponding to a predetermined incident anglerange. In the capture of the radiographic image at each position, theimage processing unit 45 performs necessary processes, such as a gaincorrection process, an offset correction process, and a defective pixelcorrection process, for the image information obtained by the radiationdetector 42 to generate a radiographic image (projection image) with,for example, a RAW format. Then, the generated radiographic image istransmitted to the image processing device 50. The tomographic imagegeneration unit 68 performs image processing, such as FBP, for theradiographic image to generate a tomographic image. As such, in a casein which only the tumor mass has been detected, it is not necessary toperform 2D imaging since the size of the tumor mass is relatively large.Only tomosynthesis imaging is performed. Therefore, it is possible toreduce a burden on the subject W caused by the compression of the breastN and to obtain necessary radiographic images (projection images andtomographic images). After tomosynthesis imaging is performed, theprocess proceeds to Step 115.

In Step 115, the radiography device control unit 46 determines whetherthe generation of a two-dimensional image is set. Specifically, forexample, in a case in which the radiography device control unit 46 setsthe two-dimensional image generation unit 70 to generate atwo-dimensional image from the tomographic image obtained bytomosynthesis imaging in advance, that is, the determination result is“Yes”, the process proceeds to Step 117. In a case in which thegeneration of a two-dimensional image is not set in advance, that is,the determination result is “No”, a series of processes ends. As such,it is possible to selectively generate a two-dimensional image, insteadof performing 2D imaging. In addition, the radiography device controlunit 46 sets whether to generate a two-dimensional image or not inadvance. However, the user may change the settings through the displaydevice 80.

In Step 117, the two-dimensional image generation unit 70 generates atwo-dimensional image and a series of processes ends.

In Step 121, the radiography device control unit 46 performstomosynthesis imaging. That is, similarly to Step 119, tomosynthesisimaging is performed while the radiation emitting unit 24 (radiationsource 30) is moved in a predetermined incident angle range. Aftertomosynthesis imaging, the process proceeds to Step 124, with the breastbeing compressed.

In Step 124, the radiography device control unit 46 performs 2D imagingand a series of processes ends. After 2D imaging is completed, thefixation of the breast by the compression plate 26 is released. Forexample, the compression plate 26 is moved in a direction in which itbecomes further away from the imaging surface 20 to release the fixationof the breast. That is, similarly to Step 116, the binning process isnot performed and a high-resolution radiographic image is generated. Ina case in which a calcification and a tumor mass have been detected,tomosynthesis imaging and 2D imaging are performed to obtain necessaryradiographic images (projection images and tomographic images). Inaddition, 2D imaging is performed under predetermined imaging conditionsto capture a radiographic image.

As such, the mutation site suspected as a lesion is detected on thebasis of the pre-irradiation image and whether to perform each oftomosynthesis imaging and 2D imaging is controlled on the basis of thedetection result. Therefore, it is possible to obtain an accurateradiographic image while reducing a burden on the subject. Inparticular, the effect of the process according to this example will bedescribed in detail. In a case in which a mutation site has not beendetected, it is not necessary to perform tomosynthesis imaging and 2Dimaging since the two-dimensional image of the breast has already beenobtained by pre-irradiation. Therefore, it is possible to provide a moreaccurate radiographic image while further reducing a burden on thesubject, as compared to the first example. In a case in which only themutation site suspected as a calcification has been detected, it isnecessary to observe the position and shape of the calcification indetail. Therefore, the detailed imaging conditions (exposure conditions)are adjusted on the basis of the result of pre-irradiation and only 2Dimaging is performed. In a case in which only the mutation sitesuspected as a tumor mass has been detected, tomosynthesis imaging isperformed since it is necessary to observe the three-dimensionalstructure of the tumor mass. Since the projection image is obtained bytomosynthesis imaging and the two-dimensional image has already beenobtained by pre-irradiation, it is not necessary to newly perform 2Dimaging. When two-dimensional image generation (combination) isperformed, it is possible to provide an accurate radiographic imagewhile reducing a burden on the subject. In a case in which both themutation site suspected as a calcification and the mutation sitesuspected as a tumor mass have been detected, both tomosynthesis imagingand 2D imaging are performed since it is necessary to observe both thecalcification and the tumor mass in detail. Therefore, it is possible toobtain sufficient data for the subsequent detailed examination.

The process according to this example controls whether to perform eachof tomosynthesis imaging and 2D imaging on the basis of the result ofpre-irradiation, regardless of resolution. Therefore, the process canalso be applied to a radiography device that can perform tomosynthesisimaging, using not the radiation detector 42 acquiring image informationitems with different resolutions but a general radiation detector(particularly, a radiation detector acquiring image information withsingle resolution).

As an example derived from the process according to this example, in acase in which the determination result in Step 106 is “No”, control maybe performed such that Step 115 and Step 117 are provided and atwo-dimensional image is generated according to settings, or control maybe performed such that only Step 117 is provided and a two-dimensionalimage is automatically generated. In addition, as another examplederived from the process according to this embodiment, in a case inwhich the determination result in Step 106 is “No”, control may beperformed such that Steps 110 and 112 in the first example are providedand an inquiry about whether 2D imaging is performed is made accordingto settings, or control may be performed such that only Step 112 isprovided and an inquiry about whether 2D imaging is performed isautomatically made.

As still another example derived from the process according to thisexample, control may be performed such that Step 115 and Step 117 areomitted after Step 119 and a two-dimensional image is not generated. Inaddition, as yet another example derived from the process according tothis example, control may be performed such that only Step 117 isprovided after Step 119 and a two-dimensional image is automaticallygenerated.

As still yet another example derived from the process according to thisexample, the radiography device control unit 46 may perform control suchthat the radiation detector 42 performs the binning process duringpre-irradiation and the radiation detector 42 does not perform thebinning process during tomosynthesis imaging and 2D imaging. In thiscase, the radiographic image generation unit generates a low-resolutionradiographic image, using pre-irradiation, generates a high-resolutionprojection image, using tomosynthesis imaging, and generates ahigh-resolution radiographic image (two-dimensional image), using 2Dimaging.

The radiography device control unit 46 performs control on the basis ofeach of the above-mentioned derivation examples and the other componentsoperate on the basis of this example.

In this embodiment, the processes according to the first and secondexamples have been individually described. The technical scope of theinvention is not limited to this embodiment. For example, the firstexample, the second example, and the individual derivation examples maybe appropriately combined with each other. Processes (for example, thedisplay of the projection image and the transmission of the tomographicimage to the outside) which do not relate to the radiography methodaccording to the invention may be inserted into each step, which is alsoincluded in the technical scope of the invention. In particular, in FIG.7B or FIG. 9, for example, a process which displays the pre-irradiationimage in a step of stopping (ending) imaging in a case in which nomutation site is detected is included in the technical scope of theinvention (that is, “stop imaging”).

In the processes according to the first and second examples, the usermay set whether each step is performed in advance. In addition, controlmay be performed such that the user is asked whether each step isperformed before it is performed. In particular, the radiography devicecontrol unit 46 may perform control such that an inquiry about whethertomosynthesis imaging or 2D imaging is performed is given to the userimmediately before tomosynthesis imaging or 2D imaging is performed andimaging starts in response to an imaging start instruction from theuser. This function can also be applied to two-dimensional image. Inthis case, an inquiry about whether imaging is performed and thereception of the instruction are performed through the display device80.

The first incident angle is not limited to the vertical direction. Thefirst incident angle may be an incident angle which is used to acquire afirst projection image during tomosynthesis imaging illustrated in FIG.2 or FIG. 3 (particularly, a in FIG. 3). Similarly, the predeterminedincident angle during 2D imaging is not limited to the verticaldirection.

In this embodiment, the resolution of the radiation detector 42 canswitch between two types and the incident angle range duringtomosynthesis imaging can switch between two types. However, theinvention is not limited thereto. For example, each of the resolutionand the incident angle range may switch between three or more types. Inparticular, in a case in which the binning process is performed in thememory, it is possible to obtain three or more types of radiographicimages. In this case, the binning process may be performed in theinternal memory of the radiation detector 42 or the memory used by theimage processing unit 45 (for example, the memory in the radiographydevice control unit 46).

The technique described in this embodiment can also be applied to aradiography device in which at least two or more types of resolution andat least two or more types of incident angle range are set. In addition,a case in which the radiation detector 42 uses the binning process hasbeen described as an example in which the radiographic image generationunit generates a low-resolution or high-resolution radiographic image.However, the invention is not limited thereto. For example, as describedabove, the radiation detector 42 may perform the thinning-out processand the radiographic image generation unit may generate alow-resolution/high-resolution radiographic image.

In this embodiment, it is determined whether the mutation site is amutation site suspected as a calcification or a mutation site suspectedas a tumor mass on the basis of the size of the mutation site detectedby the part-of-interest detection unit 47. However, the determinationmethod is not limited thereto. For example, the above-mentionedembodiment can be applied as long as the part-of-interest detection unithas a function which can determine whether the mutation site is amutation site suspected as a calcification or a mutation site suspectedas a tumor mass, using a known CAD technique (for example, the techniquedisclosed in JP2001-8923A). In this case, an example of the “mutationsite suspected as a calcification” is a “mutation site with a first sizein a predetermined range”. An example of the “mutation site suspected asa tumor mass” is a “mutation site with a size greater than the firstsize”. An example of the “mutation site suspected as a calcification orthe mutation site suspected as a tumor mass” is a “mutation site with asize equal to or greater than the first size in the predeterminedrange”.

The radiation in this embodiment is not particularly limited. Forexample, X-rays or γ-rays may be applied.

For example, the structure and operation of the radiation detector 42described in this embodiment are illustrative and can be changedaccording to circumstances, without departing from the scope and spiritof the invention.

What is claimed is:
 1. A radiography device that is capable ofperforming tomosynthesis imaging, comprising: a radiation emitting unitthat is capable of irradiating a subject with radiation at a pluralityof different incident angles; a radiographic image generation unit thatreceives the radiation which has been emitted from the radiationemitting unit and passed through the subject and generates aradiographic image indicating the subject; a part-of-interest detectionunit that detects a mutation site suspected as a lesion from theradiographic image of the subject which is obtained by irradiating thesubject with the radiation emitted from the radiation emitting unit at apredetermined incident angle; and a radiography device control unit thatcontrols, on the basis of a detection result of the part-of-interestdetection unit, whether to perform each of the tomosynthesis imaging inwhich the radiographic image generation unit generates a radiographicimage while the radiation emitting unit changes the incident angle ofthe radiation, and two-dimensional radiography in which the radiationemitting unit is fixed to a predetermined incident angle and theradiographic image generation unit generates a radiographic image. 2.The radiography device according to claim 1, wherein the radiographydevice control unit performs control such that the tomosynthesis imagingis not performed and the two-dimensional radiography is performed in acase in which the part-of-interest detection unit detects only themutation site suspected as a calcification, and the radiography devicecontrol unit performs control such that the two-dimensional radiographyis not performed and the tomosynthesis imaging is performed in a case inwhich the part-of-interest detection unit detects only the mutation sitesuspected as a tumor mass.
 3. The radiography device according to claim2, wherein the radiography device control unit further performs controlsuch that both the tomosynthesis imaging and the two-dimensionalradiography are performed in a case in which the part-of-interestdetection unit detects both the mutation site suspected as acalcification and the mutation site suspected as a tumor mass.
 4. Theradiography device according to claim 3, wherein the radiography devicecan generate the radiographic images with at least two types ofresolution, and the radiography device control unit performs controlsuch that the two-dimensional radiography is performed at a secondresolution higher than a first resolution in a case in which theradiographic image of the subject is acquired at the first resolutionand the part-of-interest detection unit detects at least one of themutation site suspected as a calcification or the mutation sitesuspected as a tumor mass from the radiographic image of the subject. 5.The radiography device according to claim 4, wherein the radiographydevice control unit further performs control such that the tomosynthesisimaging is performed at the second resolution higher than the firstresolution in a case in which the part-of-interest detection unitdetects the mutation site suspected as a tumor mass.
 6. The radiographydevice according to claim 2, further comprising: a two-dimensional imagegeneration unit that generates a two-dimensional image of the subject onthe basis of a tomographic image of the subject obtained by thetomosynthesis imaging, wherein the radiography device control unitperforms control such that the two-dimensional radiography is notperformed and the two-dimensional image generation unit generates thetwo-dimensional image of the subject in a case in which thepart-of-interest detection unit detects only the mutation site suspectedas a tumor mass.
 7. The radiography device according to claim 1, whereinthe radiography device control unit performs control such that thetwo-dimensional radiography is not performed and the tomosynthesisimaging is performed in a case in which the part-of-interest detectionunit does not detect the mutation site.
 8. The radiography deviceaccording to claim 7, wherein the radiography device can perform thetomosynthesis imaging in at least two types of incident angle ranges,(a) the radiography device control unit performs control such that thetwo-dimensional radiography is not performed and the tomosynthesisimaging is performed in a first incident angle range in a case in whichthe part-of-interest detection unit does not detect the mutation site,(b) the radiography device control unit performs control such that thetomosynthesis imaging is not performed and the two-dimensionalradiography is performed in a case in which the part-of-interestdetection unit detects only the mutation site suspected as acalcification, (c) the radiography device control unit performs controlsuch that the two-dimensional radiography is not performed and thetomosynthesis imaging is performed in a second incident angle rangewider than the first incident angle range in a case in which thepart-of-interest detection unit detects only the mutation site suspectedas a tumor mass, and (d) the radiography device control unit performscontrol such that the tomosynthesis imaging is performed in the secondincident angle range and the two-dimensional radiography is performed ina case in which the part-of-interest detection unit detects both themutation site suspected as a calcification and the mutation sitesuspected as a tumor mass.
 9. The radiography device according to claim8, wherein (a1) the radiography device control unit performs controlsuch that the tomosynthesis imaging is performed at a first resolutionand in the first incident angle range in a case in which thepart-of-interest detection unit does not detect the mutation site, (b1)the radiography device control unit performs control such that thetwo-dimensional radiography is performed at a second resolution higherthan the first resolution in a case in which the part-of-interestdetection unit detects only the mutation site suspected as acalcification, (c1) the radiography device control unit performs controlsuch that the tomosynthesis imaging is performed at the secondresolution higher than the first resolution and in the second incidentangle range wider than the first incident angle range in a case in whichthe part-of-interest detection unit detects only the mutation sitesuspected as a tumor mass, and (d1) the radiography device control unitperforms control such that the tomosynthesis imaging is performed at thesecond resolution and in the second incident angle range and thetwo-dimensional radiography is performed at the second resolution in acase in which the part-of-interest detection unit detects both themutation site suspected as a calcification and the mutation sitesuspected as a tumor mass.
 10. The radiography device according to claim1, wherein the radiography device control unit performs control suchthat neither the two-dimensional radiography nor the tomosynthesisimaging is performed and imaging is stopped in a case in which thepart-of-interest detection unit does not detect the mutation site. 11.The radiography device according to claim 1, wherein thepart-of-interest detection unit detects a mutation site with a firstsize in a predetermined range as the mutation site suspected as acalcification and detects a mutation site with a size greater than thefirst size as the mutation site suspected as a tumor mass.
 12. Aradiography method that is performed in a radiography device which iscapable of performing tomosynthesis imaging and comprises a radiationemitting unit that is capable of irradiating a subject with radiation ata plurality of different incident angles and a radiographic imagegeneration unit that receives the radiation which has been emitted fromthe radiation emitting unit and passed through the subject and generatesa radiographic image indicating the subject, the method comprising:detecting a mutation site suspected as a lesion from the radiographicimage of the subject which is obtained by irradiating the subject withthe radiation emitted from the radiation emitting unit at apredetermined incident angle; and controlling, on the basis of adetection result of the detecting step, whether to perform each of thetomosynthesis imaging in which the radiographic image generation unitgenerates a radiographic image while the radiation emitting unit changesthe incident angle of the radiation, and two-dimensional radiography inwhich the radiation emitting unit is fixed to a predetermined incidentangle and the radiographic image generation unit generates aradiographic image.
 13. The radiography method according to claim 12,wherein control is performed such that the tomosynthesis imaging is notperformed and the two-dimensional radiography is performed in a case inwhich only the mutation site suspected as a calcification is detected,and control is performed such that the two-dimensional radiography isnot performed and the tomosynthesis imaging is performed in a case inwhich only the mutation site suspected as a tumor mass is detected. 14.The radiography method according to claim 13, wherein control is furtherperformed such that both the tomosynthesis imaging and thetwo-dimensional radiography are performed in a case in which both themutation site suspected as a calcification and the mutation sitesuspected as a tumor mass are detected.
 15. The radiography methodaccording to claim 14, wherein the radiography device can generate theradiographic images with at least two types of resolution, and controlis performed such that the two-dimensional radiography is performed at asecond resolution higher than a first resolution in a case in which theradiographic image of the subject is acquired at the first resolutionand at least one of the mutation site suspected as a calcification orthe mutation site suspected as a tumor mass is detected from theradiographic image of the subject.
 16. The radiography method accordingto claim 15, wherein control is further performed such that thetomosynthesis imaging is performed at the second resolution higher thanthe first resolution in a case in which the mutation site suspected as atumor mass is detected.
 17. The radiography method according to claim13, wherein the radiography device further includes a two-dimensionalimage generation unit that generates a two-dimensional image of thesubject on the basis of a tomographic image of the subject obtained bythe tomosynthesis imaging, and control is performed such that thetwo-dimensional radiography is not performed and the two-dimensionalimage generation unit generates the two-dimensional image of the subjectin a case in which only a mutation site suspected as a tumor mass isdetected.
 18. The radiography method according to claim 12, whereincontrol is performed such that the two-dimensional radiography is notperformed and the tomosynthesis imaging is performed in a case in whichthe mutation site is not detected.
 19. The radiography method accordingto claim 18, wherein the radiography device can perform thetomosynthesis imaging in at least two types of incident angle ranges,(a) control is performed such that the two-dimensional radiography isnot performed and the tomosynthesis imaging is performed in a firstincident angle range in a case in which the mutation site is notdetected, (b) control is performed such that the tomosynthesis imagingis not performed and the two-dimensional radiography is performed in acase in which only the mutation site suspected as a calcification isdetected, (c) control is performed such that the two-dimensionalradiography is not performed and the tomosynthesis imaging is performedin a second incident angle range wider than the first incident anglerange in a case in which only the mutation site suspected as a tumormass is detected, and (d) control is performed such that thetomosynthesis imaging is performed in the second incident angle rangeand the two-dimensional radiography is performed in a case in which boththe mutation site suspected as a calcification and the mutation sitesuspected as a tumor mass are detected.
 20. The radiography methodaccording to claim 19, wherein (a1) control is performed such that thetomosynthesis imaging is performed at a first resolution and in thefirst incident angle range in a case in which the mutation site is notdetected, (b1) control is performed such that the two-dimensionalradiography is performed at a second resolution higher than the firstresolution in a case in which only the mutation site suspected as acalcification is detected, (c1) control is performed such that thetomosynthesis imaging is performed at the second resolution higher thanthe first resolution and in the second incident angle range wider thanthe first incident angle range in a case in which only the mutation sitesuspected as a tumor mass is detected, and (d1) control is performedsuch that the tomosynthesis imaging is performed at the secondresolution and in the second incident angle range and thetwo-dimensional radiography is performed at the second resolution in acase in which both the mutation site suspected as a calcification andthe mutation site suspected as a tumor mass are detected.
 21. Theradiography method according to claim 12, wherein control is performedsuch that neither the two-dimensional radiography nor the tomosynthesisimaging is performed and imaging is stopped in a case in which themutation site is not detected.
 22. The radiography method according toclaim 12, wherein a mutation site with a first size in a predeterminedrange is detected as the mutation site suspected as a calcification anda mutation site with a size greater than the first size is detected asthe mutation site suspected as a tumor mass.
 23. A non-transitorystorage medium storing a program that causes a computer to execute aradiography processing, the radiography processing comprising: detectinga mutation site suspected as a lesion from a radiographic image of asubject which is obtained by irradiating the subject with radiationemitted from a radiation emitting unit of a radiography device capableof performing tomosynthesis imaging at a predetermined incident angle;and controlling, on the basis of a detection result of the detectingstep, whether to perform each of the tomosynthesis imaging in which aradiographic image generation unit of the radiography device generates aradiographic image while the radiation emitting unit changes theincident angle of the radiation, and two-dimensional radiography inwhich the radiation emitting unit is fixed to a predetermined incidentangle and the radiographic image generation unit generates aradiographic image.